Non-CICS Attachments

Analysis of CPU use in non-CICS environments (IMS, TSO, CAF, batch, and utilities) must take several factors into account:

  • thread status
  • specific attachment environment

OMEGAMON® XE for DB2 PE reports CPU use for the actual MVS TCB (subtask) that owns the active DB2 thread. SRB time is not included.

Thread Status

Unlike the CICS® attachment, non-CICS environments typically contain a single DB2 thread. Recognizing the status of that thread will help you determine whether the reported CPU use can be attributed to Db2 request activity.

For example, if thread status is In-SQL-Call, the CPU rate reported is indeed related to Db2 thread activity. However, if the thread status is Not-In-DB2, you can conclude that the CPU rate reported is attributable to application activity that is unrelated to Db2, although the application indeed still owns a Db2 thread (for example, an IMS transaction doing DL/I requests).

Attachment Environment

The non-CICS attachment environments vary in the MVS task structure they use to service DB2 threads. Thus, your analysis must take into account the attachment type in use.

For example, an IMS attachment does not result in the creation of an MVS subtask to service a thread. In a TSO environment, however, an additional MVS TCB is created to service each thread.

The following examples explain the ways in which thread status, Db2 version, and attachment environment jointly affect your interpretation of the OMEGAMON XE for DB2 PE CPU use data.

Example 1

In a TSO attachment environment using SPUFI, program DSN is attached as an MVS daughter subtask in the TSO address space. The DSN subtask then attaches program DSNECP10, which is a daughter subtask of the DSN subtask. The DSNECP10 subtask is the actual MVS TCB that owns the DB2 thread. As a result, it is the CPU use of this MVS task that is being reported by OMEGAMON XE for DB2 PE.

If thread status indicates Not-In-DB2, OMEGAMON XE for Db2 PE will report that CPU use (MVS TCB CPU use) is 0.

Example 2

In an IMS environment, the IMS attachment does not attach a new MVS subtask to service the Db2 thread. As a result, the CPU use reported for IMS threads can reflect CPU time that is attributable to non-DB2 work. This means that you must take into account the status of the DB2 thread, as discussed above.

Example 3

Assume an application that creates multiple Db2 threads (executing concurrently), using the Db2 call attach facility (CAF).

The reported CPU use of a thread is always attributable to the MVS task that owns that thread. And you must consider the thread's status to determine whether the reported CPU use is attributable to DB2 or to non-DB2 application activity.