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Status Not under consideration
Workspace CICS Transaction Server for z/OS
Categories Runtime
Created by Guest
Created on May 4, 2023

RELATED IDEAS

Allow DFHJVM* logs to roll based on file size

We recently upgraded to CICS 6.1 and encountered an unexpected log message from a Liberty JVM. It wasn't frequent enough to trigger alarms in test, but did once it went to production, filling our logging partition. We attempted to delete the massive files, but the JVM held on to them somehow and they kept increasing in size (despite not being visible to the OS).

We have an open support case for this, but a root cause is that the DFHJVM* log files only roll on CICS or JVM restarts. I suggest rolling log files based on a maximum file size configuration would greatly help. E.g. MAX_LOG_SIZE=100MB and then make a new log file once the old one hits 100MB+. Viewing a massive log file is almost impossible anyway.

Idea priority Urgent
  • Guest
    Reply
    |     May 25, 2023
    CICS Development: The particular error that was causing the logs to fill was cause by a failure in the container iterator, which is a regression and APAR PH54360 has been raised to fix this.

    As for rolling logs, although nice to have, they would only mask a fundamental problem. CICS offers alternative approaches to managing these files.

    The development effort to implement dynamic output file switching - and then to coordinate such updates between our internal logging components (Assembler, C, Java, OSGi and Liberty) - is currently very large compared to the modest functional gain. We currently have higher priority items taking our focus, so the idea is being declined.

    CICS offers alternative approaches to managing these files (see below).

    Supporting information:

    dfhjvmout is the standard output stream, it's content is written by customer applications, not CICS
    dfhjvmerr reports errors and exceptions, if the file size grows it is an indication that immediate application fixes are required, or there is a internal error that requires attention from IBM service
    dfhjvmlog contains essential events and messages which should be finite except where repeated errors are occurring, guidance is as above. However, you can also control the granularity of the messages that go to this file with the LOG_LEVEL= INFO | WARNING | ERROR | NONE parameter in the JVM profile.
    dfhjvmtrc is only produced when SJ and AP domain trace levels are set greater than 2, this should not be used in production and is an IBM service diagnostic.
  • Guest
    Reply
    |     May 11, 2023
    The particular error that was causing the logs to fill was cause by a failure in the container iterator, which is a regression and APAR PH54360 has been raised to fix this.

    As for rolling logs, although nice to have, they would only mask a fundamental problem. CICS offers alternative approaches to managing these files.

    dfhjvmout is the standard output stream, it's content is written by customer applications, not CICS
    dfhjvmerr reports errors and exceptions, if the file size grows it is an indication that immediate application fixes are required, or there is a internal error that requires attention from IBM service
    dfhjvmlog contains essential events and messages which should be finite except where repeated errors are occurring, guidance is as above. However, you can also control the granularity of the messages that go to this file with the LOG_LEVEL= INFO | WARNING | ERROR | NONE parameter in the JVM profile.
    dfhjvmtrc is only produced when SJ and AP domain trace levels are set greater than 2, this should not be used in production and is an IBM service diagnostic.

    The development effort to implement dynamic output file switching - and then to coordinate such updates between our internal logging components (Assembler, C, Java, OSGi and Liberty) - is currently very large compared to the modest functional gain. We currently have higher priority items taking our focus.

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