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New DB2z "LOCKMAXCANCEL" tablespace characteristic - cancel thread when N locks have been reached

Suggest a new parameter for the TABLESPACE definition (perhaps named "LOCKMAXCANCEL").

LOCKMAXCANCEL

This would allow you to specific a number that represent the maximum number of locks that can be acquired for the tablespace at which point the thread would be cancelled (i.e. resource unavailable).

  • Seth Bienstock
  • Dec 15 2018
  • Need More Information
Why is it useful?
Who would benefit from this IDEA?
How should it work?

Proposed Solution:

A new sub-parameter of LOCKMAX, coded as follows:

LOCKMAX nnnn CANCELTHREAD

When a non-zero value is supplied for LOCKMAX, you can optionally code "CANCELTHREAD" which would mean that instead of lock escalation occurring, the thread is cancelled.

Measurable Benefits:

There have been times where a call results in too many locks being taken on a heavily referenced table and the thread continues for too long thereby locking other threads out. This is usually caused by poor application design/coding, and sometimes just due to the (state of) the data at the time. For those infrequent, but costly, occasions where this occurs, this capability would help prevent this from happening.

Current Work Around:

None at this time.

Considered customizing a third-party monitoring tool to identify the situation and cancel the thread. This would result in additional overhead and would probably be a bear to maintain from a DBA/admin perspective.

Idea Priority Low
Priority Justification
Customer Name Morgan Stanley
Submitting Organization
Submitter Tags
  • Attach files
  • Seth Bienstock commented
    28 May 12:42pm

    NUMLKUS is usually coded at a very high level and counts the total number of lock for the thread. I would like a parameter at a lower level - TABLESPACE - that behaves differently than LOCKMAX. Presently, lock escalation is the only effect of LOCKMAX. After that, you are depending upon NUMLKUS, which might be too high for your purposes.

    This new parameter would be at the TABLESPACE level, and would specify a number of locks acquired at which point the thread would be cancelled - no lock escalation.

  • Admin
    Janet Figone commented
    29 Jan 07:51pm

    Could you please add more information - why the current NUMLKUS does not work for you. Today, we have NUMLKUS zparm to specify the max locks held per thread. Exceeding the value will receive resource unavail (SQLCODE -904 and message DSNT500I or DSNT501I are issued. ). thanks.

  • and 16 more

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