How to reduce the amount of SMF 110 records

Learn about how to respond when you notice an occasional huge increase in SMF 110 records that CICS TS writes and about the techniques for reducing the number of records CICS TS writes to SMF.

Cause

An increase in the number of transactions results in an increase in the number of performance monitoring 110 records.

What to do

  1. Find out what type of SMF 110 records CICS is writing. Both the CICS statistics and the CICS monitoring (CMF) records are written as SMF type 110 records, but they are different subtypes.
    For the statistics records
    Check whether interval statistics is turned on and check the length of the interval. If the interval is set very low, then more statistics will be written more frequently, which will increase the volume of SMF 110 records. You can display the interval using CEMT INQ STAT.
    For the monitoring records
    Check whether performance monitoring is turned on and whether you are using a customized MCT so as to reduce the number of fields reported. You can display the monitoring setting with the CEMN transaction. CEMN gives you an alternative to the INQUIRE MONITOR and SET MONITOR system programming commands and the equivalent CEMT INQ MON command.
  2. CICS performs data compression, by default, on the SMF 110 monitoring records produced by the CICS monitoring facility (CMF). Data compression can provide a significant reduction in the volume of data written to SMF.

    You can specify which performance monitoring records are to be compressed. Data compression only applies to SMF 110 records written by CICS monitoring, with subtype X'0001' in the record subtype field in the SMF header. It does not apply to the other types of SMF 110 records created by CICS, such as records written by CICS journaling, CICS statistics, the TS data sharing server, the coupling facility data table ( CFDT ) server, and the named counter sequence number server. For details, see Data compression for monitoring records.

    Note: When you display the monitoring settings with CEMN, try turning data compression on if it's not already on to see if that helps. If you turn on data compression, you have to be sure that any programs that you use to process the performance monitoring records can handle the compressed records.

    You can turn on compression all the time by defining an monitoring control table (MCT) that specifies COMPRESS=YES. You can use the IBM-supplied MCT sample DFHMCT2$ as a base for your own MCT. If you do not use a feature like DBCTL for example, then you can remove or comment out the COPY DFH$MCTD statement. You can then use the DFHAUPLE procedure to link edit and create your MCT.

    If you just want to use the default MCT and do nothing except use data compression, you can use the example in Figure 1 in DFHMCT examples.

  3. You can exclude monitoring groups that you do not use so as to reduce the amount of data written to SMF. For more information, see The monitoring control table (MCT).