Today, it is easy to validate that a bound query is used as a hint to a static query. After all, there is a column updated in PLAN_TABLE when the package is bound that exploits the bound query.
But, it becomes difficult to know if a dynamic query actually uses the bound query as a hint and/or to know if all the dynamic queries that were using the bound query as a hint are now no longer running.
It would be nice if either there was a new column (LASTUSED) placed on the SYSIBM.SYSQUERY table that would store the date that the query was used for a hint AND/OR it would be really nice if the DSN_STATEMENT_CACHE_TABLE were extended with an additional column that indicated that the row for the query used a bound query as a hint (there would be no need for a date here, because the CACHED_TS column would indicate when the hint was used.
We are using the REOPT(ONCE) option for our NULLID.* packages (basically, the connect driver packages). There are times that we need to hint a query to the DEFAULT access path that would be used for host variables. When I install one of these hints, it is rather hard to detect if the hint was actually used or if I just got lucky and the access path happened to be the DEFAULT access path. Having a tracking mechanism for the use of one of these hints would help us to know that we did the right thing.
Also, sometimes the application changes a query that was once hinted. We would really like to know when one of these hints is no longer used.
Why is it useful?
|Who would benefit from this IDEA?||DBAs and developers that work with tuning queries.|
How should it work?
One (or both) of the tables mentioned above should be changed. And the new column should be populated with appropriate values by Db2.
|Priority Justification||This has been a struggle for us.|
|Customer Name||Mutual of Omaha|
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