CICS performance degradation with increase in DB2 signon activity and DB2 SMF records

If the increase in CICS DB2 signon activity and flood of new DB2 SMF records coincided with a BIND or REBIND on a PLAN or PACKAGE, and you specified an OPTHINT parameter value of spaces, the problem is documented by DB2 APAR PI39860 (RA10, 10.1) which has a title of "Signon count very high for CICS plans / packages specifying OPTHINT(' ')."

APAR PI39860 is still OPEN at this time. For now, you can use the following "Local Fix" which is documented in PI39860:

To get around this issue, remove the OPTHINT(' ') specification. This can be done by a BIND PLAN or BIND PACKAGE with the REPLACE and RETAIN keywords, and by not specifying the OPTHINT keyword.

Below are some of the diagnostics that we've seen when looking at a dump of a CICS region:

If CICS RI component level 2 trace is active, you see a signon event traced for every transaction using the package/plan. Trace entries will look similar to the following:

 AP 3260 D2D2  EVENT ABOUT_TO_ISSUE_DB2_SIGNON_WITH_PRIMARY_AUTH(XXXXX )   
 AP 3261 D2D2  EVENT RETURN_FROM_DB2_SIGNON_WITH_PRIMARY_AUTH(XXXXX )  

In the fully formatted AP 3260 trace entries, the data traced as parameter 4 is the DFHD2CSB control block. In a CICS 670 (4.2) release, the following two fields in this block are relevant:

CSB_THREAD_CREATED is x'04' bit at byte x'B4' in CSB.

CSB_INITIAL_STATE is x'40' bit at byte x'B4' in CSB.

When this problem occurs, CSB_THREAD_CREATED bit is on, but CSB_INITIAL_STATE bit is off.