Method and system for log management in a coupled data processing system

Abstract

In a coupled data processing system having multiple users, either in a single system or in a multi-system environment, a coupling facility storage structure is used to provide a log management facility. The log management facility provides for a real time physical log merge of the data written into the log stream without interprocessor communication required to process the records in logical sequence. The log management facility supports concurrent write, delete, browse, and asynchronous off-load to dasd processes across multi-users and multi-systems. The log management facility maintains the log records, independent of the log media, in time sequence. A logical block id is assigned to each log record written so that it can be directly accessed at a later time.

Claims

What is claimed is:

1. A method for managing log data in a data processing system comprising a plurality of processors, said method comprising:

writing, by said plurality of processors, a plurality of data records to a log stream, said log stream comprising at least a portion of a coupling facility storage structure residing within a coupling facility, said coupling facility sharable by said plurality of processors and comprising a processor and a communications facility, said writing comprising:

providing a real-time merge of said plurality of data records in a particular sequence, said providing comprising performing serialization for said log stream at said coupling facility, wherein said plurality of processors are relieved of providing said serialization for said log stream.

2. The method of claim 1, wherein said providing comprises writing said plurality of data records to said log stream in time sequence.

3. The method of claim 2, wherein said providing comprises:

determining a value for a list authority control; and

using said value to place said plurality of data records within said log stream in time sequence.

4. The method of claim 2, further comprising retrieving one or more of said plurality of data records using a selected time stamp.

5. The method of claim 1, further comprising determining a logical identifier for each of said plurality of data records, wherein each of said plurality of data records has a respective logical identifier, each logical identifier representing a logical offset into said log stream.

6. The method of claim 5, wherein each logical identifier represents a key for direct access to its respective data record when said respective data record resides in said at least a portion of said coupling facility storage structure.

7. The method of claim 5, wherein said log stream further comprises one or more data sets and wherein each logical identifier is usable in direct access of its respective data record when said respective data record resides in one of said one or more data sets.

8. The method of claim 1, wherein said at least a portion of said coupling facility storage structure comprises a list.

9. The method of claim 1, further comprising concurrently performing a function against said log stream being written to while maintaining integrity of said log stream.

10. The method of claim 9, wherein said function comprises one of the following functions: a write function, a delete function, a read function and an off-load function.

11. The method of claim 1, wherein said log stream further comprises one or more data sets and said method further comprises off-loading one or more of said plurality of data records from said at least a portion of said coupling facility storage structure to said one or more data sets.

12. The method of claim 11, wherein said off-loading comprises:

reading one or more data records from said at least a portion of said coupling facility storage structure;

storing in an input/output buffer a predetermined amount of said one or more data records read from said at least a portion of said coupling facility storage structure; and

writing said input/output buffer to said one or more data sets when said predetermined amount of said one or more data records is stored in said input/output buffer.

13. The method of claim 12, further comprising repeating said storing and writing until said one or more data records read from said at least a portion of said coupling facility storage structure has been stored in said input/output buffer.

14. The method of claim 13, further comprising deleting from said at least a portion of said coupling facility storage structure said one or more data records read from said at least a portion of said coupling facility storage structure after said one or more data records is written to said one or more data sets.

15. The method of claim 11, further comprising off-loading said one or more data records until a predefined low threshold of resources has been attained for said at least a portion of said coupling facility storage structure.

16. A system for managing log data in a data processing system comprising a plurality of processors, said system comprising:

a log stream comprising at least a portion of a coupling facility storage structure residing within a coupling facility, said coupling facility sharable by said plurality of processors and comprising a processor and a communications facility, said coupling facility being adapted to provide serialization for said log stream, wherein said plurality of processors is relieved of providing said serialization for said log stream; and

means for writing, by said plurality of processors, a plurality of data records to said log stream in a particular sequence, wherein a real-time merge of said plurality of data records is provided.

17. The system of claim 16, wherein said means for writing comprises means for writing said plurality of data records to said log stream in time sequence.

18. The system of claim 17, wherein said means for writing comprises:

means for determining a value for a list authority control; and

means for using said value to place said plurality of data records within said log stream in time sequence.

19. The system of claim 17, further comprising means for retrieving one or more of said plurality of data records using a selected time stamp.

20. The system of claim 16, further comprising means for determining a logical identifier for each of said plurality of data records, wherein each of said plurality of data records has a respective logical identifier, each logical identifier representing a logical offset into said log stream.

21. The system of claim 20, wherein each logical identifier represents a key for direct access to its respective data record when said respective data record resides in said at least a portion of said coupling facility storage structure.

22. The system of claim 20, wherein said log stream further comprises one or more data sets and wherein each logical identifier is usable in direct access of its respective data record when said respective data record resides in one of said one or more data sets.

23. The system of claim 16, wherein said at least a portion of said coupling facility storage structure comprises a list.

24. The system of claim 16, further comprising means for concurrently performing a function against said log stream being written to while maintaining integrity of said log stream.

25. The system of claim 24, wherein said function comprises one of the following functions: a write function, a delete function, a read function and an off-load function.

26. The system of claim 16, wherein said log stream further comprises one or more data sets and said system further comprises means for off-loading one or more of said plurality of data records from said at least a portion of said coupling facility storage structure to said one or more data sets.

27. The system of claim 26, wherein said means for off-loading comprises:

means for reading one or more data records from said at least a portion of said coupling facility storage structure;

an input/output buffer storing a predetermined amount of said one or more data records read from said at least a portion of said coupling facility storage structure; and

means for writing said input/output buffer to said one or more data sets when said predetermined amount of said one or more data records is stored in said input/output buffer.

28. The system of claim 27, further comprising means for deleting from said at least a portion of said coupling facility storage structure one or more data records read from said at least a portion of said coupling facility storage structure after said one or more data records is written to said one or more data sets.

29. The system of claim 26, further comprising means for off-loading said one or more data records until a predefined low threshold of resources has been attained for said at least a portion of said coupling facility storage structure.

30. A method for logging information in a data processing system comprising a first processor executing a first application and a second processor executing a second application, said method comprising:

said first application writing a first record to a log stream; and

said second application writing a second record to said log stream, said first and second applications writing independently of each other such that application serialization during said writing of said first record and said second record is not necessary, and wherein the writing of the first and second records provides a real-time merge of said first record and said second record in a predetermined logical sequence.

31. The method of claim 30, further comprising determining prior to writing said second record if said second record can be written to said log stream in said predetermined logical sequence.

32. The method of claim 31, wherein said predetermined logical sequence comprises ascending time order and wherein said determining comprises performing a list authority comparison, wherein said second record is not written when said list authority comparison is unsuccessful.

33. The method of claim 32, wherein said performing comprises:

comparing a comparative list authority operand with a list authority control to determine if a predefined relationship exists between said comparative list authority operand and said list authority control.

34. The method of claim 33, wherein said predefined relationship comprises a less than or equal operation.

35. The method of claim 30, further comprising assigning a first identifier to said first record and a second identifier to said second record, said first and second identifiers indicating the logical sequence of said first and second records in said log stream, said first identifier and said second identifier representing logical offsets into said log stream for direct access of said first record and said second record, respectively.

36. The method of claim 35, wherein said assigning is performed independently of other functions processing against said log stream.

37. The method of claim 35, further comprising using said first identifier during one or more operations requiring direct access to said first record.

38. The method of claim 37, wherein said one or more operations comprises one of deleting said first record from the log stream and reading said first record in the log stream.

39. The method of claim 35, wherein said log stream comprises at least a portion of a coupling facility storage structure and one or more data sets, and wherein said first identifier is usable in direct access of said first record regardless of its location in said at least a portion of said coupling facility storage structure and said one or more data sets.

40. The method of claim 30, wherein said first application and said second application each writes a plurality of records to said log stream in said predetermined logical sequence.

41. The method of claim 30, wherein said log stream comprises a portion of a coupling facility storage structure and one or more data sets and said method further comprises reading said log stream to read one of said first and second records regardless of its location in said at least a portion of said coupling facility storage structure and said one or more data sets.

42. The method of claim 30, further comprising:

assigning, by said first processor, a first identifier to said first record as part of said writing of said first record; and

assigning, by said second processor, a second identifier to said second record as part of said writing of said second record, wherein said first processor assigns said first identifier and said second processor assigns said second identifier without communicating with each other about the assigning of the first and second identifiers.

43. The method of claim 42, wherein said assigning said first identifier comprises setting said first identifier equal to an assignment variable.

44. The method of claim 43, further comprising:

determining an increment value; and

updating said assignment variable by said increment value, wherein the updated assignment variable comprises said second identifier.

45. The method of claim 30, wherein said log stream comprises a coupling facility list structure and one or more data sets.

46. A method for assigning identifiers to data records within a data processing system, said method comprising:

dynamically determining a unique identifier for a record to be written to a stream of records, said identifier being in logical sequence with any other identifiers associated with said stream of records and representing a logical relative offset into said stream of records for direct access of said record, wherein said identifier is determined independently of other functions being processed against said stream of records; and

assigning said identifier to said record when said record is written to said stream of records.

47. The method of claim 46, wherein said other functions comprises one of a write function, a delete function, a read function and an off-load function.

48. The method of claim 46, wherein said stream of records comprises at least a portion of a coupling facility storage structure and a data set, and wherein said identifier is usable in direct access of said record, regardless of whether said record is stored in said coupling facility storage structure or said data set.

49. The method of claim 46, wherein said assigning comprises setting said identifier equal to an assignment variable.

50. The method of claim 49, further comprising:

determining an increment value; and

updating said assignment variable by said increment value, wherein the updated assignment variable comprises a next identifier to be assigned.

51. A system for logging information in a data processing system, said system comprising:

a first processor adaptable to write a first record to a log stream; and

a second processor adaptable to write a second record to said log stream, said first and second processors being adaptable to write independently of each other such that application serialization during said writing of said first record and said second record is not necessary, and wherein the writing of the first and second records provides a real-time merge of said first record and said second record in a predetermined logical sequence.

52. The system of claim 51, further comprising means for determining prior to writing said second record if said second record can be written to said log stream in said predetermined logical sequence.

53. The system of claim 52, wherein said predetermined logical sequence comprises ascending time order and wherein said means for determining comprises means for performing a list authority comparison, wherein said second record is not written when said list authority comparison is unsuccessful.

54. The system of claim 53, wherein said means for performing comprises:

means for comparing a comparative list authority operand with a list authority control to determine if a predefined relationship exists between said comparative list authority operand and said list authority control.

55. The system of claim 54, wherein said predefined relationship comprises a less than or equal operation.

56. The system of claim 51, further comprising means for assigning a first identifier to said first record and a second identifier to said second record, said first and second identifiers indicating the logical sequence of said first and second records in said log stream, said first identifier and said second identifier representing logical offsets into said log stream for direct access of said first record and said second record, respectively.

57. The system of claim 56, wherein said means for assigning is performed independently of other functions processing against said log stream.

58. The system of claim 56, further comprising means for using said first identifier during one or more operations requiring direct access to said first record.

59. The system of claim 58, wherein said one or more operations comprises one of deleting said first record from the log stream and reading said first record in the log stream.

60. The system of claim 56, wherein said log stream comprises at least a portion of a coupling facility storage structure and one or more data sets, and wherein said first identifier is usable in direct access of said first record regardless of its location in said at least a portion of said coupling facility storage structure and said one or more data sets.

61. The system of claim 51, wherein said first application and said second application each writes a plurality of records to said log stream in said predetermined logical sequence.

62. The system of claim 51, wherein said log stream comprises a portion of a coupling facility storage structure and one or more data sets and said system further comprises means for reading said log stream to read one of said first and second records regardless of its location in said at least a portion of said coupling facility storage structure and said one or more data sets.

63. The system of claim 51, wherein:

said first processor is adaptable to assign a first identifier to said first record as part of said writing of said first record; and

said second processor is adaptable to assign a second identifier to said second record as part of said writing of said second record, and wherein said first processor assigns said first identifier and said second processor assigns said second identifier without communicating with each other about the assigning of the first and second identifiers.

64. The system of claim 63, wherein said assigning said first identifier comprises means for setting said first identifier equal to an assignment variable.

65. The system of claim 64, further comprising:

means for determining an increment value; and

means for updating said assignment variable by said increment value, wherein the updated assignment variable comprises said second identifier.

66. The system of claim 51, wherein said log stream comprises a coupling facility list structure and one or more data sets.

67. A system for assigning identifiers to data records within a data processing system, said system comprising:

means for dynamically determining a unique identifier for a record to be written to a stream of records, said identifier being in logical sequence with any other identifiers associated with said stream of records and representing a logical relative offset into said stream of records for direct access of said record, wherein said identifier is determined independently of other functions being processed against said stream of records; and

means for assigning said identifier to said record when said record is written to said stream of records.

68. The system of claim 67, wherein said other functions comprises one of a write function, a delete function, a read function and an off-load function.

69. The system of claim 67, wherein said stream of records comprises at least a portion of a coupling facility storage structure and a data set, and wherein said identifier is usable in direct access of said record, regardless of whether said record is stored in said coupling facility storage structure or said data set.

70. The system of claim 67, wherein said means for assigning comprises means for setting said identifier equal to an assignment variable.

71. The system of claim 70, further comprising:

means for determining an increment value; and

means for updating said assignment variable by said increment value, wherein the updated assignment variable comprises a next identifier to be assigned.

Description

TECHNICAL FIELD

This invention relates, in general, to logging information in a data processing system, and in particular, to providing log management services in a coupled data processing system which enables the concurrent processing of main line functions by multiple users in either a single system or multi-system environment.

CROSS REFERENCE TO RELATED APPLICATIONS

This application contains subject matter which is related to the subject matter of the following applications which are assigned to the same assignee as this application. Each of the below listed applications is hereby incorporated by reference in its entirety:

"Configurable, Recoverable Parallel Bus," by N. G. Bartow et al., Filed: Feb. 20, 1992 now U.S. Pat. No. 5,357,608;

"High Performance Intersystem Communications For Data Processing Systems," by N. G. Bartow et al., Filed: Feb. 20, 1992 now U.S. Pat. No. 5,412,803;

"Frame-Group Transmission And Reception For Parallel/Serial Buses," by N. G. Bartow et al., Filed: Feb. 20, 1992, now U.S. Pat. No. 5,267,240;

"Communicating Messages Between processors And A Coupling Facility," by D. A. Elko et al., Filed: Mar. 30, 1992 now abandoned;

"Sysplex Shared Data Coherency Method And Means," by D. A. Elko et al., Filed: Mar. 30, 1992 now U.S. Pat. No. 5,537,574;

"Method And Apparatus For Distributed Locking of Shared Data, Employing A Central Coupling Facility," by D. A. Elko et al., Filed: Mar. 30, 1992 now U.S. Pat. No. 5,339,427;

"Command Quiesce Function," by D. A. Elko et al., Filed: Mar. 30, 1992 now U.S. Pat. No. 5,339,405;

"Storage Element For A Shared Electronic Storage Cache," by D. A. Elko et al., Filed: Mar. 30, 1992 now U.S. Pat. No. 5,457,793;

"Management Of Data Movement From A SES Cache To DASD," by D. A. Elko et al., Filed: Mar. 30, 1992 now U.S. Pat. No. 5,493,668;

"Command Retry System," by D. A. Elko et al., Filed: Mar. 30, 1992 now U.S. Pat. No. 5,392,397;

"Integrity Of Data Objects Used To Maintain State Information For Shared Data At A Local Complex," by D. A. Elko et al., Filed: Mar. 30, 1992 now U.S. Pat. No. 5,331,673;

"Management Of Data Objects Used To Maintain State Information For Shared Data At A Local Complex," by J. A. Frey et al., Filed: Mar. 30, 1992 now U.S. Pat. No. 5,388,266;

"Recovery Of Data Objects Used To Maintain State Information For Shared Data At A Local Complex," by J. A. Frey et al., Filed: Mar. 30, 1992 now U.S. Pat. No. 5,399,542;

"Message Path Mechanism For Managing Connections Between Processors And A Coupling Facility," by D. A. Elko et al., Ser. No. 07/860,646, Filed: Mar. 30, 1992 now abandoned;

"Method And Apparatus For Notification Of State Transitions For Shared Lists Of Data Entries," by J. A. Frey et al., Ser. No. 07/860,809, Filed: Mar. 30, 1992 now U.S. Pat. No. 5,390,328;

"Method And Apparatus For Performing Conditional Operations On Externally Shared Data," by J. A. Frey et al., Ser. No. 07/860,655, Filed: Mar. 30, 1992 now abandoned;

"Apparatus And Method For List Management In A Coupled Data Processing System," by J. A. Frey et al., Filed: Mar. 30, 1992 now U.S. Pat. No. 5,410,695;

"Interdicting I/O And Messaging Operations In A Multi-System Complex," by D. A. Elko et al., Filed: Mar. 30, 1992 now U.S. Pat. No. 5,394,554;

"Method And Apparatus For Coupling Data Processing Systems," by Elko et al., Filed: Mar. 30, 1992, now U.S. Pat. No. 5,317,739;

"Authorization Method For Conditional Command Execution," by Elko et al., Ser. No. 08/021,285, Filed: Feb. 22, 1993, now abandoned.

"A Dumping Service Facility For Multisystem Environment," by Elko et al., Ser. No. 08/073,909, Filed: Jun. 08, 1993, now abandoned;

"A Method And System For Capturing and Controlling Access To Information In A Coupling Facility," by Neuhard et al., Ser. No. 08/146,647, Filed Nov. 01, 1993, now U.S. Pat. No. 5,630,050;

"A Method And System For Managing Data and Users of Data in a Data Processing System," by Allen et. al., Ser. No. 08/146,727, Filed Nov. 01, 1993, now U.S. Pat. No. 5,465,359;

"A Method And System For Managing One or More Coupling Facilities in a Data Processing System," by Allen et. al., Ser. No. 08/148,075, Filed Nov. 01, 1993, now abandoned; and

"A Structure Rebuild Method and System," by Allen et al., Ser. No. 08/146,635, Filed Nov. 1, 1993, now abandoned.

BACKGROUND ART

In a loosely coupled data processing environment, multiple instances of an application requiring data logging facilities, such as a distributed data base manager, may be distributed across multiple systems within the data processing environment. Each instance executing in parallel with other instances, and each instance requiring update access to shared resources (e.g., data bases). For instance, consider a data base being shared by multiple instances of an application, each distributed instance requiring full/equal access to the shared resource with integrity.

To guarantee data integrity, parallel applications log multiple types of data. One type of log data tracks the progress of a transaction (the resources it has changed) such that the modifications performed by the transaction can be backed out to a consistent state should the transaction not complete successfully. A second type of log data tracks updates to physical recording media (e.g., dasd) such that the recording media can be restored to a consistent state in the event of media failure (e.g., dasd head crash).

Applications use one of the following methods for logging data to maintain the integrity of shared resources:

1. Each parallel instance writes its corresponding log data to a log data set, the log data set fully accessible by each parallel instance of the application. Since multiple parallel instances of the application are writing to the same log data set, four problems arise: performance, bandwidth, serialization and synchronization. Each of these problems is discussed below:

Performance is affected because only one parallel instance of the application can be writing log data at any one time; other parallel instances with log data to write must wait until the current writer completes its log writes.

Bandwidth is affected because of the current limits of how much data can be transferred to dasd in a unit of time. Writes to dasd are asynchronous events. Current methods of hardening are limited by the number of I/Os that can be processed per second and the contention resulting from the control unit overhead created by servicing multiple operating system instances in parallel. Dasd subsystem performance can be further aggravated by the failure to write the data sequentially.

Serialization is affected because the log data set must reflect the time sequence in which data base updates were applied so that they can be recovered with integrity. To insure this ordering requirement, the instance of the application must hold serialization that blocks its distributed instances from performing concurrent writes to the log data set.

Synchronization is affected because the instance of the parallel application that has filled up a data set must inform all other instances that they are to now write log data to a different log data set.

2. Each distributed instance writes log data to its own unique set of log data sets. When recovery action is required for a shared resource, the set of instance-specific log data created by all parallel instances of the application that share the resource must be merged to provide a time-sequenced view of the activity against a shared resource so that recovery actions can be successful. When recovery actions are required, installation personnel must intervene to find the appropriate set of shared log data sets, merge them and then initiate recovery utilities. This solution also shares the performance and bandwidth problems previously discussed.

In addition, real time browsing is not practical because of the need to merge the log data requiring systems to be quiesced.

3. Another mechanism includes partitioning the data base. This means that each parallel instance of the application is the exclusive owner of a piece of the data base. Should a transaction it is processing need to access a part of the data base it does not own, then its request must be sent to the parallel instance that owns that part of the data base. As with the previous examples, performance and bandwidth are negatively affected. Recovery is also complex as multiple instances of log data sets must be merged to produce a time-sequenced ordering of data base updates.

Regardless of which option an application implements, each parallel instance of an application requires the following:

1. A set of application-specific definitions that tell the distributed instance of the application the set of log data sets to which it is to record log data.

2. Knowledge of the underlying log recording media and associated access method. For example, dasd media using the Virtual Sequential Access Method (VSAM) access method.

3. The application must know the set of data sets (one or more) on which the log data resides, must be able to create new data sets as log data sets reach capacity, must have ways to read log data to initiate recovery processing, and must have ways to delete log data (and log data sets) that are no longer needed.

4. The ability to allocate and deallocate log data sets as required.

As more and more applications become distributed, each unique application must implement a logging function, much of it very similar to what other applications have already implemented. Correspondingly, the systems management overhead increases as an installation must also specify unique logging definitions to each distributed application.

Based on the foregoing, a need exists for a mechanism for distributed instances of an application to log data to a common set of log data sets that provides a real time merge of log data, acceptable performance, high bandwidth, reduced recovery time and acceptable systems management characteristics.

SUMMARY OF THE INVENTION

The shortcomings of the prior art are overcome and additional advantages are realized through the provision of a log management facility. In accordance with the principles of the present invention, a method and system for managing log data within a data processing system is provided. A plurality of data records are written to a log stream, which comprises at least a portion of a coupling facility storage structure. The data records are arranged in a particular sequence.

In one embodiment, the portion of the coupling facility storage structure is a coupling facility list and the data records are arranged in time sequence. A list authority comparison is used to maintain the time sequence. In another example, the log stream comprises one or more data sets as well as the coupling facility list.

Each record in the log stream has a logical block id for use in accessing the record in the log stream. This logical block id is used to access a record in the list or within the data sets, which provides for direct access to individual records for the purpose of browsing or deleting records in the log stream.

In a further aspect of the invention, key assignment is performed. The key assignment represents the next valid block id to be assigned. The key assignment process enables the assignment of the next block id to be used without having to understand intervening write activity to the log stream by other applications. That is, the key assignment process is independent of other activity against the log stream. No interprocessor communication is required in order to generate the key or perform key assignment processing.

Additionally, the log management facility of the present invention advantageously provides a multi-system dynamic merge of log stream data, high performance and high bandwidth. The merge of the present invention is a real-time physical merge of the log data in logical sequence. The records in the log stream are maintained in logical sequence by timestamp and relative block address (i.e., block id) regardless of whether the data is resident in the coupling facility or on dasd. The log management facility encapsulates the logging function in one operating system component, relieving distributed applications that require logging of having to design and develop their own logging subcomponents. A user application is unaware of the underlying implementation and corresponding topology. It greatly simplifies systems management activities and automatically controls the backup and archiving of log data sets. It eliminates the need for stand alone batch utilities to sort/merge logs so that recovery operations can be performed. It also hides data set specific items from the user application: i.e., allocation and deallocation of data sets, access methods, I/O error recovery, and tracking of the set of individual data sets that comprise a log stream.

In one embodiment, the system logger of the present invention uses lists within a coupling facility list structure to provide a real time log merge function that dynamically merges the log data generated by multiple instances of an application.

Other advantages of the system logger include, for example, the high performance hardening of data, measured in micro-seconds rather than milli-seconds; high bandwidth when writing data to a recording media; and the use of atomic processes or functions, such as write, browse, delete and off-load functions. Further, the system logger provides the ability to concurrently write, browse, and delete information to and from the log stream with integrity. Each of the concurrent processes may be performed across multi-users and/or multi-systems within a data processing environment, without interfering with each other.

Additionally, a writer off-load process may be concurrently performed with the other functions described above (e.g., write, read, delete) without interference and while maintaining integrity. The writer off-load process provides efficient space management in dasd and minimizes dasd contention.

Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 depicts one example of a block diagram of a data processing system incorporating the log merger services of the present invention;

FIG. 2 depicts one example of a list structure, in accordance with the principles of the present invention;

FIG. 3 depicts one example of the controls associated with the list structure of FIG. 2, in accordance with the principles of the present invention;

FIG. 4 depicts one example of the controls associated with a list within the list structure of FIG. 2 used in accordance with the principles of the present invention;

FIG. 5 illustrates one example of a list entry control block, in accordance with the principles of the present invention;

FIG. 6 depicts one example of a message command/response block, in accordance with the principles of the present invention;

FIG. 7 depicts one embodiment of request/response operands, in accordance with the principles of the present invention;

FIG. 8 depicts one embodiment of the logic associated with connecting to a log stream, in accordance with the principles of the present invention;

FIG. 9 depicts one embodiment of the logic associated with a worker task processing a request received during the connect processing of FIG. 8, in accordance with the principles of the present invention;

FIG. 10 illustrates one example of the logic associated with writing log blocks to a log stream, in accordance with the principles of the present invention;

FIG. 11 illustrates one example of a data element being written from a writer off-load control list header to a writer off-load initiative list header, in accordance with the principles of the present invention;

FIG. 12 depicts one example of the logic associated with transitioning list information from the coupling facility to dasd during writer off-load processing, in accordance with the principles of the present invention;

FIG. 13 depicts one example of the logic associated with processing of a service request block, which was scheduled during the list transitioning process of FIG. 12, in accordance with the principles of the present invention;

FIGS. 14a-14d depict one example of the logic associated with writing data entries to a dasd data set during the service request block processing of FIG. 13, in accordance with the principles of the present invention;

FIGS. 15a-15k depict one embodiment of the logic associated with reading log blocks in the log stream, in accordance with the principles of the present invention;

FIG. 15l depicts one embodiment of a browse token and its associated session state information, in accordance with the principles of the present invention;

FIG. 16 illustrates one embodiment of the logic associated with deleting a log block from a log stream, in accordance with the principles of the present invention;

FIGS. 17a-17b depict one example of the logic associated with disconnecting from a log stream, in accordance with the principles of the present invention;

FIGS. 18a-18b illustrate one example of the logic associated with assignment key request processing, in accordance with the principles of the present invention;

FIG. 19 depicts one embodiment of an application connecting to a log stream and writing log blocks to the log stream, in accordance with the principles of the present invention; and

FIG. 20 depicts one embodiment of an application browsing log blocks in a log stream and deleting from a log stream, in accordance with the principles of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a block diagram of a data processing system 10 incorporating the log management services of the present invention. In one example, data processing system 10 includes multiple central processing complexes (CPCs) 12a through 12n which are coupled to an input/output (I/O) system 14 and a coupling facility 16. (As used herein, central processing complexes 12a-12n are collectively referred to as central processing complex (CPC) 12.) The main components associated with each central processing complex 12, input/output system 14 and coupling facility 16 are described in detail below. (While the invention is described in relation to a multisystem environment, such as the one depicted in FIG. 1, it can also be used with a single system environment, which includes one central processing complex 12.)

Each of the CPCs 12a-12n may be an International Business Machines' (IBM) system following the Enterprise Systems Architecture/390 Principles of Operation as described in IBM publication SA22-7201-00, which is hereby incorporated by reference in its entirety. Each of CPCs 12a-12n includes one or more central processing units (CPUs) (not shown) which executes an operating system 13a-13n, respectively. As used herein, operating systems 13a-13n are collectively referred to as operating system 13. In one instance, operating system 13 is an International Business Machines' Multiple Virtual Storage (MVS) operating system for controlling execution of programs and the processing of data, as is well known. In addition, in accordance with the principles of the present invention, each operating system 13a-13n includes a Cross-System Extended Services (XES) facility (not shown) for managing and accessing information in a coupling facility, and the log management facility of the present invention 15a-15n, respectively.

In addition, each CPC 12a-12n contains a plurality of intersystem (I/S) channels 18a-18n, a plurality of local storage 20a-20n, and a plurality of input/output (I/O) channels 22a-22n, respectively. (Intersystem channels 18a-18n and input/output channels 22a-22n are collectively referred to as intersystem channels 18 and input/output channels 22, respectively.) It will be understood that input/output channels 22 are part of the well known channel subsystem (CSS), which also includes intersystem channels 18 disclosed herein, even though channels 18 and 22 are shown separately in FIG. 1 for convenience.

Coupled to each CPC 12a-12n is an external time reference (ETR) 24, which provides time stamps of control information to be written into a log to document recovery from failures, backing out of undesired operations and for audit trails. External time reference 24, which uses fiber optic interconnect cables, synchronizes the time clocks (not shown) of CPCs 12a-12n to a precision equal to or greater than the duration of the shortest externally visible operation. External time reference 24 provides for cable length propagation time differences, where those differences are important, in order to be able to maintain synchronization to within the length of the mentioned external operation.

As depicted in FIG. 1, each central processing complex 12a-12n is coupled via a link 26a-26n, respectively, to input/output system 14. Input/output system 14 includes, for example, a dynamic switch 28, which controls access to multiple input/output (I/O) control units (CU) 30a through 30n and one or more direct access storage devices (DASD) D1 through DN (collectively referred to as dasd 32), which are controlled by the control units. Dynamic switch 28 may be an ESCON Director Dynamic Switch available from IBM Corporation, Armonk, N.Y. Such a dynamic switch is disclosed in U.S. patent application Ser. No. 07/429,267 for "Switch and its Protocol," filed Oct. 30, 1989, now U.S. Pat. NO. 5,107,489, and assigned to the owner of the present invention, which application is incorporated herein by reference in its entirety. As is known, input/output commands and data are sent from a central processing complex 12a-12n to an I/O control unit 30a-30n through dynamic switch 28 by means of I/O channels 22a through 22n of the respective CPCs 12a through 12n. Channel programs for a particular I/O channel are established by channel command words (CCWs), as is well known in the art.

One or more of direct access storage devices 32 includes one or more data sets 31a-31n, respectively. In accordance with the principles of the present invention, the data sets are used for storing data off-loaded from the coupling facility when a particular threshold is met. The off-loading of data is described in detail below.

Each central processing complex 12a-12n is also coupled via a bus 34a-34n, respectively, to coupling facility 16. Coupling facility 16 contains storage accessible by the CPCs, performs operations requested by programs in the CPCs and maintains status regarding structures and users of structures located within the coupling facility. The coupling facility enables sharing of data, which is directly accessible by multiple operating systems. In one embodiment, coupling facility 16 is a structured-external storage (SES) processor and includes, for example, a plurality of intersystem (I/S) channels 36 for communicating with intersystem channels 18a-18n, one or more buffers 38 located within intersystem channels 36 for storing data received from intersystem channels 18a-18n, message processors 40a-40n for handling messages, a selector 44 for directing message requests received over an intersystem channel to a message processor 40a-40n, and one or more storage structures 48, each of which is described in further detail below. Even though only one coupling facility 16 is shown in the embodiment of FIG. 1, it will be understood that multiple coupling facilities may be provided for, each with its own I/S channels and message paths connected to all or some subset of the CPCs 12a-12n.

One example of a storage structure 48 located in the coupling facility is a list structure 52, an embodiment of which is depicted in FIG. 2 and described in detail below.

Referring to FIG. 2, in one example, coupling facility 16 is coupled to processor storage 90a-90n located within each CPC 12a-12n, respectively. List structure 52 includes list-structure controls 92, and, optionally, a lock table 96, and/or a list set 98. List set 98 includes list controls 100 and list-entry controls 102. Each of the components of list structure 52 is described in detail below.

List structure controls 92 contain attributes of the structure and are initialized when list structure 52 is created. One example of the controls associated with list structure controls 92 is depicted in FIG. 3. Referring to FIG. 3, list structure controls 92 include, for example:

(a) Maximum Data-List-Entry Size (MDLES): An object or field that specifies the maximum size of the data list entry.

(b) List-Structure Type (LST): An object or field that indicates the list objects created on allocation. The field contains a counter indicator (CI), a lock indicator (LI), a data indicator (DI), an adjunct indicator (AI), a name indicator (NI) and a key indicator (KI).

The counter indicator specifies that either: a list-entry count and list-entry-count limit are defined or a list-element count and list-element-count limit are defined.

The lock indicator specifies whether or not a lock table is created.

The data and adjunct indicators specify whether: no list-set is created; list entries have adjunct only; list entries have data only; or list entries have data and adjunct in the list entries.

The name indicator specifies whether or not list entries are named.

The key indicator specifies whether or not the list entries are keyed.

(c) Lock-Table-Entry Characteristic (LTEX): An object or field that specifies the number of bytes in each lock-table entry. The number of bytes is the product of 2 raised to the power of the LTEX value.

(d) List-Element Characteristic (LELX): An object or field that specifies the number of bytes in each list element. The number of bytes is the product of 256 and 2 raised to the power of the LELX value.

(e) Minimum Structure Size (MNSS): A value that specifies the minimum number of units of SES storage that can be allocated for the list.

(f) Lock-Table-Entry Count (LTEC): An object or field that specifies the number of lock-table entries allocated.

(g) List Count (LC): An object or field that specifies the number of lists created.

(h) Structure Size (SS): An object or field that specifies the amount of storage allocated.

(i) Maximum Structure Size (MXSS): A value that specifies the maximum number of units of SES storage that can be allocated for the list.

(j) Maximum List-Set-Element Count (MLSELC): An object or field that specifies the maximum number of list elements that are available for assignment to list entries or retry-data blocks, or both, in the list set.

(k) List-Set-Element Count (LSELC): An object or field that specifies the number of list elements that have been assigned to list entries or retry-data blocks, or both, in the list set.

(l) Maximum List-Set-Entry Count (MLSELC): An object or field that specifies the maximum number of possible list entries in a list set.

(m) List-Set-Entry Count (LSEC): An object or field that specifies the number of existing list entries in the list set.

Referring once again to FIG. 2, lock table 96 consists of a sequence of one or more lock table entries 97 identified by a lock-table-entry number (LTEN). In one embodiment, lock table entry 97 includes a lock-table-entry number (LTEN), which starts at zero and runs consecutively and a lock-table-entry value (LTEV), including a global-lock manager (GLM) object and optionally, a local-lock-manager (LLM) object or both. The lock-table entry format is determined by the list-structure type located within list structure controls 92.

Commands associated with list structure 52 provide a means for updating lock-table entry 97. That is, a command may compare global-lock managers (GLM) and conditionally replace a global-lock manager (GLM), a local-lock manager (LLM), or both the global-lock and local-lock managers (GLM) and (LLM). The list commands also provide a means for reading an entry in lock-table 96 or the next non-zero lock-table entry, or for clearing lock table 96.

As previously mentioned, also contained within list structure 52 is list set 98. In one example, list set 98 includes one or more lists 99 represented by list controls 100, which are numbered consecutively, starting at zero. In one embodiment, list controls 100 include the following controls, as depicted in FIG. 4:

(a) Assignment Key (AK): In accordance with the principles of the present invention, an assignment key is provided. It is an object or field that specifies the value assigned to a list-entry key when a key-assignment operation is executed for a list entry that is moved or created on the list. The assignment key is initialized to zeros.

(b) Assignment Key Threshold (AKT): In accordance with the principles of the present invention, an assignment key threshold is provided. It is an object or field that specifies the maximum value of an assignment key. The assignment key threshold is initialized to zeros.

(c) List-Entry-Count Limit (LECL): An object or field that specifies the maximum number of possible list entries in a list. This object is initialized to the maximum list-set-entry count when a list structure is created.

(d) List-Element-Count Limit (LELCL): An object or field that specifies the maximum number of possible list elements in a list. This object is initialized to the maximum list-set-element count in the list-structure controls when a list structure is created.

(e) List-Entry-Count (LEC): An object or field that specifies the number of list entries currently in the list.

(f) List-Element-Count (LELC): An object or field that specifies the number of list elements currently in the list.

(g) List Authority (LAU): A value that is compared and conditionally updated. The LAU is used in accordance with the principles of the present invention to maintain the records of the log stream in time sequence.

(h) List-Monitor-Table: The list-monitor table contains information used to process the list-notification vector of each user who has registered interest in the state transitions of the list.

The list-monitor table is a sequence of objects, called list-monitor-table entries. The number of list-monitor-table entries is determined when the table is created and is equal to the maximum number of list-structure users. The list-monitor-table entries are numbered from zero to the user-identifier limit and are indexed by the user identifier (UID).

Each list-monitor-table entry has a list-monitoring-active-bit object, a list-notification-request-type object and a list-notification-entry-number object, each of which is described below:

(1) List-Monitoring-Active Bit (LMAB): An object or field that specifies whether the user associated with the list-monitor-table entry is monitoring the list-state transitions of the list.

When a user is not monitoring a list, all previously issued list-notification commands on behalf of the associated user for this list are complete.

(2) List-Notification-Request Type (LNRT): An object or field that indicates whether the list-notification-vector summaries are to be updated when an empty to not-empty state transition occurs on a monitored list.

(3) List-Notification-Entry Number (LNEN): An object or field that specifies a list-notification-vector entry.

When a list-state transition occurs, one or more list-notification commands are initiated for each user who is monitoring the list to the system which attached the user. All the list-notification commands initiated as a result of the list-state transition are initiated before the command that caused the list-structure transition is completed.

The list-notification command provides the information necessary for the system to update one list-notification entry and, when requested, the associated list-notification summaries, to reflect the new list state.

A user becomes a list monitor by registering with the list by means of a register-list-monitor command. A user ceases to be a list monitor by deregistering from the list by means of a deregister-list-monitor command or by detaching from the list structure by means of a detach-list-structure-user command.

A list-notification command issued to a system for a user as a result of a not-empty-to-empty list-state transition must complete before another list-notification command on behalf of the same list and user that specifies the opposite list-state transition may be issued.

All SES list-structure commands capable of adding, deleting, or moving a list entry execute the list-monitor-notification process for each user monitoring a list that changes state.

When a transition notification is initiated to a system, any previously initiated but unsent notifications for the same list and user may be purged.

Returning to FIG. 2, each list 99 consists of a sequence of zero or more entries. The list-structure type (described above) determines whether all the list entries in list set 98 have a data list entry 104, an adjunct list entry 106, or both. Associated with each entry of a list 99 is one of list-entry controls 102. Controls 102 contain list-entry-location information and other information for controlling operations against data list entry 104.

In particular, list entry controls 102 include, for instance, the following controls, as depicted in FIG. 5:

(a) A Data-List-Entry Size (DLES) indicating the size of the associated data entry.

(b) A List Number (LN) representing the list that a particular entry is associated with.

(c) A List-Entry Identifier (LEID) identifying a particular list entry. The list-entry identifier is unique to a list set 98 and is assigned by coupling facility 16.

(d) A Version Number (VN) object that is conditionally compared and conditionally updated, reflecting a program specified state for the list entry.

(e) An optional List-Entry Key (LEK) indicating a key, if one exists. When list-entry keys exist, the keyed list entries are ordered by the key with the lowest numerical key at the leftmost position. Elements with the same key value may be located by first or last within the same key value.

When an unkeyed list entry is created or moved, the target list-entry position is always located by an unkeyed position. When a keyed list entry is created or moved, the target list-entry position is always located by a keyed position and first or last within the same key value.

(f) An optional List-Entry Name (LEN). A list-entry name is unique to a list set 98 (FIG. 2) at any particular instant and is provided by the operating system program.

List commands provide a means for conditionally creating, reading, replacing, moving, or deleting one entry in list 99. A number of comparisons may be requested during these processes. They include a list-number comparison, a version-number comparison, a global-lock-manager (GLM) comparison, or any combination of the preceding. Additionally, when global locks are compared, local locks (LLM) may be compared. A list entry may be moved from one list 99 to another within the same structure 52 or from one position to another within the same list 99. This is disclosed in U.S. patent application Ser. No. 07/860,655 for "Method and Apparatus for Performing Conditional Operations on Externally Shared Data" by J. A. Frey, et al. (Attorney Docket No. P09-92-008), incorporated herein by reference in its entirety as noted.

The position of a list entry in list 99 is determined when it is created, and may be changed when any entry in the list is created, deleted or moved. A list entry or list-entry position is located within a list set 98 by means of the list-entry identifier or the optional list-entry name (as described above), or by position. Position is specified by means of a list number, a direction, and an optional list-entry key.

The list commands also provide a means for synchronously writing and moving, moving and reading, or reading and deleting one entry of list 99. More than one list entry may be deleted synchronously, and more than one data list entry 104 or adjunct list entry 106 may also be read synchronously. Data list entry 104 is always returned in the data area designated in main storage by a message command/response block, described below. The adjunct list entry is returned in either a message command/response block or the data area, depending on the command. This is disclosed in U.S. patent application Ser. No. 07/860,633 for "Apparatus and Method for List Management in a Coupled Data Processing System" by J. A. Frey, et al., now U.S. Pat. No. 5,410,695, incorporated herein by reference in its entirety, as noted.

In one embodiment, messages are communicated between CPC 12 and coupling facility 16 via a message command/response block 110 (FIG. 6). In one example, message command/response block 110 includes a message command block 112, a message response block 114 and an optional data block 116. Message command block 112 includes a command block 118 and a plurality of request operands 120 and message response block 114 includes a response descriptor 122 and a plurality of response operands 124. In one embodiment, request operands 120 and response operands 124 include the operands listed below, which are depicted in FIG. 7. (An operand may be a request operand, a response operand or both, depending upon the command. It is also possible that other request and/or response operands exist, which are not shown in FIG. 7.) In one embodiment, the response/request operands include the following:

(a) Assignment-Key Increment (AKI): In accordance with the principles of the present invention, an assignment-key increment is provided. It represents a value that is added to the value of the assignment key when the assignment key is updated.

This request operand is ignored unless the list entries are keyed, the assignment-key-request type is not zero, and the assignment-key-update type represents an increment.

(b) Assignment Key (AK): In accordance with the principles of the present invention, it is a value that specifies the value assigned to a list-entry key when a key-assignment operation is executed for a list entry that is moved or created on the list.

(c) Assignment-Key-Request Type (AKRT): In accordance with the principles of the present invention, it is a value that indicates when the list-entry key is set to the value of the assignment key in the list controls. In one example, the assignment-key-request type has the following states:

List-entry key not assigned

List-entry key assigned on move

List-entry key assigned on create

List-entry key assigned on create or move

This request operand is ignored unless the list entries are keyed.

(d) Assignment-Key-Update Type (AKUT): In accordance with the principles of the present invention, it is a value that indicates how the assignment key is updated. In one example, it has the following states:

Assignment key not updated increment assignment key

This request operand is ignored unless the list entries are keyed and the assignment-key request type (AKRT) is not zero.

(e) Assignment Key Threshold (AKT): In accordance with the principles of the present invention, it is a value that specifies the maximum value of an assignment key.

(f) Comparative List Authority (CLAU): A value that is compared to the list authority.

(g) Data-List-Entry Size (DLES): An object or field that specifies the size of the data list entry.

(h) List-Monitoring Active Bit (LMAB): A value that specifies whether the user associated with the list-monitor-table entry is monitoring the list-state transitions of the list. The value has one of the two following meanings: Not monitoring the list and monitoring the list. When the list-monitoring-active bit indicates that the list is not monitored, all previously issued list-notification commands on behalf of the associated user for this list are complete.

(i) List-Notification-Entry Number (LNEN): An object or field that specifies a list-notification-vector entry.

(j) List-Notification-Token (LNT): A value that specifies a list-notification vector to the system.

(k) List Authority (LAU): A value that is compared and conditionally updated. The LAU is used in accordance with the principles of the present invention to maintain the records of the log stream in time sequence.

(l) List-Authority-Comparison Type (LAUCT): In accordance with the principles of the present invention, it is a value that indicates the procedure for comparing the list authority. In one example, it has the following meanings:

Do not compare list authorities

Compare list-authority object and CLAU operand for being equal

Compare list-authority object for being less than or equal to the

CLAU operand

Invalid

This request operand is ignored unless the entry is located by keyed or unkeyed position, by list cursor, or list-number comparison is requested.

(m) List-Authority-Replacement Type (LAURT): In accordance with the principles of the present invention, it is a value that indicates the procedure for updating the list authority. In one example, it has the following meanings:

Do not replace the list authority

Replace the list-authority object

with the LAU operand

This request operand is ignored unless the entry is located by keyed or unkeyed position, by list cursor, or list-number comparison is requested.

(n) List-Control Type (LCT): A bit string consisting of consecutive list-control-update bits. Each bit is associated with a particular list control, and when one, causes the list control to be updated to a specified value. When the bit is zero, the associated list control is not updated. One example of the list controls represented by the list-control type are:

List Control

Assignment Key

Assignment Key Threshold

User-List Control

List-Element-Count Limit or List-Entry-Count Limit

The assignment key and assignment key threshold are provided in accordance with the principles of the present invention. They are ignored unless the list entries are keyed.

(o) List-Entry Type (LET): A value that indicates whether data list entries, adjunct list entries, or both are read or replaced upon normal completion of the command execution.

(p) List Number (LN): An object or field which designates the list that the list entry is in.

(q) Comparative Version Number (CVN): A value that is compared to the version number object located in list entry control block 102.

(r) Version Number (VN): An object or field that is conditionally updated. The version number is initialized to zero when a list entry is created.

(s) Comparative Global Lock Manager (CGLM): A value that is compared to the global lock manager object located in lock table 96.

(t) Local Lock Manager (LLM): A value which identifies users with local interest in the lock-table entry.

(u) Write Request Type (WRT): A value that indicates the type of write request. The write request type specifies to replace a list entry, to create a list entry, or to replace or create a list entry.

In accordance with the principles of the present invention, a system logger running in its own address space provides a set of services that allows an application to connect to and maintain a log stream of data. Each system has its own system logger. In one example, a log stream is defined as a collection of one or more log records (also referred to as log blocks) written by an application using the services provided by the system logger. In accordance with the principles of the present invention, in one example, the data for each log stream is stored within a coupling facility list structure and dasd. The media in which the data is stored is, however, transparent to the user of the system logger. The application using the system logger services may or may not have multiple instances of itself executing in a coupled system environment. If there are multiple instances of the application in a coupled data processing system, the instances may be distributed across multiple systems in the coupled system or all instances may be executing on the same system. In the example of a multi-instance application where each instance of an application writes log records to the same log stream, the result, in accordance with the principles of the present invention, is a coupled system-wide merged log stream.

In accordance with the principles of the present invention, an application can use the system logger to connect to a log stream, write data to a log stream, browse data from a log stream, delete data from a log stream and disconnect from a log stream. Each of these services is described in detail below.

In one example, in order to connect to a log stream, a service referred to as IXGCONN is used. One example of the syntax associated with an IXGCONN macro used in invoking the connect service is described in detail below. (In this example, certain of the parameters are listed as required, while others are listed as optional. This is only one example and it may be different for another embodiment.):

    ______________________________________
    ›xlabel!
          IXGCONN,  ,REQUEST=CONNECT
                 ,STREAMNAME=xstreamname
                 ,AUTH=READ
                 ,AUTH=WRITE
                 ,STREAMTOKEN=xstreamtoken
                 ,USERDATA={xuserdata.vertline.
                  NO.sub.-- USERDATA}
                 ,STRUCTNAME=xstructname
                 ,AVGBUFSIZE=xavgbufsize
                 ,MAXBUFSIZE=xmaxbufsize
                 ,ELEMENTSIZE=xelementsize
              ,REQUEST=DISCONNECT
                 ,STREAMTOKEN=xstreamtoken
                 ,FORCE=NO
                 ,FORCE=YES
                 ,USERDATA={xuserdata.vertline.
                    NO.sub.-- USERDATA}
                 ,ANSAREA=xansarea
                 ,ANSLEN=xanslen
                 ,RETCODE=xretcode
                 ,RSNCODE=xrsncode
    ______________________________________

    ______________________________________
    ›xlabel!
            IXGWRITE     ,STREAMTOKEN=xstreamtoken
                         ,BUFFER=xbuffer
                         ,BLOCKLEN=xblocklen
                         ,BUFFALET=xbuffalet.vertline.0}
                         ,BUFFKEY={xbuffkey.vertline.*}
                         ,RETBLOCKID=xretblockid
                         ,TIMESTAMP={xtimestamp.vertline.
                          NO.sub.-- TIMESTAMP}
                         ,MODE=SYNC
                         ,MODE=SYNCECB
                          ,ECB=xecb
                         ,ANSAREA=xansarea
                         ,ANSLEN=xanslen
                         ,RETCODE=xretcode
                         ,RSNCODE=xrsncode
    ______________________________________

    ______________________________________
    ›xlabel!
          IXGBRWSE  ,STREAMTOKEN=xstreamtoken
                    ,REQUEST=START
                 ,OLDEST
                 ,YOUNGEST
                 ,STARTBLOCKID={xstartblockid}
                 ,SEARCH={search}
                   ,GMT={YES.vertline.NO}
                 ,BROWSETOKEN=xbrowsetoken
              ,REQUEST=READCURSOR
                 ,BROWSETOKEN=xbrowsetoken
                 ,BUFFER=xbuffer
                 ,BUFFLEN=xbufflen
                 ,BUFFKEY={xbuffkey.vertline.*}
                 ,BUFFALET={xbuffalet.vertline.0}
                 ,BLKSIZE={xblksize.vertline.0}
                 ,DIRECTION={OLDTOYOUNG.vertline.
                   YOUNGTOOLD}
                 ,RETBLOCKID={xretblockid.vertline.
                   NO.sub.-- BLKID
                 ,TIMESTAMP={xtimestamp.vertline.
                   NO.sub.-- TIMSETAMP}
              ,REQUEST=READBLOCK
                 ,BROWSETOKEN=xbrowsetoken
                 ,BLOCKID=xblockid
                 ,SEARCH=xsearch
                   ,GMT={YES/.vertline.NO}
                 ,RETBLOCKID={xretblockid.vertline.
                   NO.sub.-- BLKID}
                 ,BUFFER=xbuffer
                 ,BUFFLEN=xbufflen
                 ,BUFFKEY={xbuffkey.vertline.*}
                 ,BUFFALET={xbuffalet.vertline.0}
                 ,BLKSIZE={xblksize.vertline.0}
                 ,TIMESTAMP={xtimestamp.vertline.
                   NO.sub.-- TI