The system logger interface - syncsort_simulate_2000 - Latest

DIF has an interface to the MVS System Logger. For an overview of the MVS System Logger, examine “Chapter 9. Planning for System Logger Applications” in the “OS/390 MVS Setting Up a Sysplex” (GC28-1779).

This interface allows the products to:

• write messages and records to the system logger.
• consolidate messages and records from DIF address spaces on multiple systems and write the data to a single log file.

Logging product data to the System Logger

Messages and records written by the rules language can be routed to the system logger using the DEFCONN rule statements. A DEFCONN statement maps a DDname requested by the WRITEREC and WRITEMSG statements to an MVS System Logger stream name. An application is provided that can be used to extract the data for later processing. For more information about the extract program, examine “The Message Facility Print Program -DIFMFPRT” on page 3-38.

Using the System Logger to consolidate log data

The system logger can also be used to establish a communication link between the DIF started tasks in a sysplex. One DIF address space is designated as the logserver, and the other DIF address spaces can pump log data to the logserver DIF using the system logger as temporary storage. The logserver DIF can then write or update records in the “real” log files.

Implementation — The MVS System Logger can be used by the products in two ways: as a repository for user log records, and as a facility where log file updates can be consolidated through a single DIF.

Message and Record Logging

DIF has always had the ability to write log messages and records from a product’s rules language to log files. Originally, this log facility was developed to provide an alternative to the SMF interface used by ACC/SRS. Since most installations typically have a great deal of SMF data, processing SMF data to extract a limited number of SRS recovery messages seemed unreasonable. Instead, DTS provided log data sets allocated in the DIF address space to route SRS recovery messages or other messages of interest. In short, one quick look at a log file would give a storage administrator a summary of the SRS recoveries that occurred the night before.

Many DTS customers took the event logging capabilities of the SCC products much further than originally intended. Also, the original DIF log architecture requires that each system maintain its own set of DIF log files. In large sysplex environments, this creates a data management problem. Any post-processing on the logs requires an application to merge log files produced by many different systems.

IBM also had many products that contained similar logging facilities: CICS, OPERLOG, LOGREC, APPC/MVS and IMS. In recent years, IBM generalized the log interface to be shared by these and any other vendor and/or user application. DTS products can also use the MVS System Logger, which is now available on all OS/390 systems.

The DIF interface to the system logger is very easy to establish, and can be completely transparent to the SCC product rules already developed by your installation. To route messages and/or records to the system log, establish a connection with the DEFCONN command or DEFCONN statement. While the statement can be placed in a product’s rules language, it would normally be executed external to the rules with the EXEC CONNECT statement used in DIFINIT.

For example, use the DTS.R71.PARMLIB(DIFINIT) member to execute an EXEC(CONNECT(member)) command. The DEFCONN commands processed by EXEC CONNECT establish the connection to reroute messages and records to an MVS system logger stream name. For example, DIFINIT might contain:

INITOPT EXEC(CONNECT(LOGINIT))
    

The LOGINIT member should contain the DEFCONN statements required to route specific log data to the system logger. The LOG option can be specified on the DEFCONN statement to copy log records to both the local DD statement as well as the system logger stream. A sample DTS.R71.PARMLIB(LOGINIT) member follows:

DEFCONN ACCLOG  LOGGER(DTS.LOGGER.STREAM)
DEFCONN SCCACL  LOGGER(DTS.LOGGER.STREAM LOG)
    

Since all DIF started tasks probably share the same DIF PARMLIB DD statement, this simple change should activate the system logger facility for the ACCLOG and SCCACL files.

Using the System Logger to Consolidate Log Records

When multiple DIF address spaces are active in your sysplex, the system logger can be used to consolidate log records to a single data set. Multiple systems can be writing messages to the logger’s stream name, but one DIF can be assigned to extract the messages from the system logger and then write the records to the log data set.

ABC provides a perfect example. If ABC is running on multiple systems in your sysplex to track data set usage for ABARS backups, record updates can be routed to the log server DIF which has control of the ABCVSAM database. Without consolidated updates, each image in the sysplex would require an associated ABCVSAM database to avoid VSAM share problems, and each ABC utility would have to merge input data from multiple databases.

In the following example, the system logger is used to perform log record consolidation. The DIF commands would be placed in the DIFINIT member in DTS.R71.PARMLIB. In the example, log records are routed through the system logger to SYSA which will be the log server used for record consolidation.

SYSID(EXCLUDE(SYSA))
INITOPT EXEC(CONNECT(LOGINIT)) SYSID(INCLUDE(SYSA))
INITOPT LOGSERVER(LOGGER(DTS.STREAM)) SYSID()
    

The first SYSID section executes on all systems except SYSA and would execute the DEFCONN commands in member LOGINIT to establish connectors which route records to the system logger. The LOGINIT contains the DEFCONN commands to capture an I/O request made to a DDname, and reroute records to a logger stream. For more information, examine “EXEC” on page 6-9 in the Product Installation Guide. Note: No DD statements for the logs are required in these DIF started tasks unless the LOG parameter is specified on DEFCONN statements. A sample DTS.R71.PARMLIB(LOGINIT) member:

DEFCONN ACCLOG  LOGGER(DTS.STREAM)
DEFCONN ABCDB   LOGGER(DTS.STREAM)
DEFCONN RTMDB   LOGGER(DTS.STREAM)
    

The second SYSID section would only execute on SYSA and activates the log server to gather records from the system logger and write them to the target logs. For more information, examine “LOGSERVER” on page 6-11 in the Product Installation Guide. The last SYSID() terminates conditional command processing.

Setup Required to use the System Logger

The OS/390 System Logger is currently used by many system components: CICS, OPERLOG, LOGREC, APPC/MVS and IMS. By default, most OS/390 systems will have the system logger installed and running.

The setup steps required to use the system logger with DTS products requires only the definition of a log stream name. There are two types of streams available for system logs: DASD-only log streams and coupling facility log streams. A DASD-only log stream has a single-system scope; only one system at a time can connect to a DASD-only log stream.

Therefore, DASD-only logs would not normally be used with DTS products in a sysplex environment. A coupling facility log stream can contain data from multiple systems, allowing a system logger application (DIF) to merge data from systems across the sysplex.

The following sample JCL can be used to define a new structure and coupling facility log stream to the system logger. The sample JCL can be found in the DIF sample distribution library: DTS.R71.SLyyddd.SAMPLIB(IXCMIAPU). Fields represented in bold type may need to be modified before submission.

 //jobname JOB ... (RC=0 EXPECTED)
 //STEP1   EXEC PGM=IXCMIAPU
 //SYSPRINT DD SYSOUT=*
 //SYSIN   DD *
 DATA TYPE(LOGR) REPORT(YES)
 DEFINE STRUCTURE NAME(DTS_STRUCTURE) LOGSNUM(32)
 DEFINE LOGSTREAM NAME(DTS.STREAM) STRUCTNAME(DTS_STRUCTURE) LIST
 LOGSTREAM NAME(DTS.STREAM) DETAIL(YES)
 LIST STRUCTURE NAME(DTS_STRUCTURE) DETAIL(YES)
 //*
    

Figure 4-1. JCL to Create a System Logger Streamname