Timing information

The Accounting report set provides a multitude of timing information for nondistributed and distributed transactions.

OMEGAMON for Db2 Performance Expert reports the following timing information:

• Application times (class 1)
• DB2 times (class 2)
• Suspension times (class 3) and counts
• IFI times (class 5)
• DB2 times on a per package/DBRM basis (class 7)
• Suspensions times on a per package/DBRM basis (class 8) and counts

If an Accounting record represents an allied-distributed thread, additional time fields for DDF data are reported. These DDF times are obtained from Accounting class 1.

The following figure shows an example of the DB2 Accounting times for a nondistributed transaction that does not exploit CP parallelism and how the Accounting times relate to each other and to the DB2 SQL call activity. The example depicts an application for IMS or CICS®. Classes 5, 7, 8, and 9 are not shown. Class 5 is a subset of class 2 and is present only if IFI processing takes place. Classes 7 and 8 are equivalent to classes 2 and 3, but on a package or DBRM level.

The following figure shows various elapsed times for a distributed transaction originating from TSO allied space. CP parallelism is not exploited. The times for both the requester and the server are shown. This figure is a simplified presentation of the processes at the participating locations. It does not, for example, show block fetch statements and it is only applicable to a single row retrieval. DDF-at-Server time is not provided if the transaction uses DRDA.

The various elapsed times in the figure are defined as follows:

• DDF at Server

  This is the ELAPSED SER field that is reported in the Requester Fields for Server Location section of the Accounting reports and traces. It represents the elapsed time spent at the server between the time the SQL statement is received and the time the answer is sent to VTAM®. This time is not applicable to DRDA and N/A is printed.

• DDF at Requester

  This is the ELAPSED REQ field in the Server Fields for Requester Location section of the Accounting reports and traces. It represents the elapsed time spent at the requester between the time the SQL statement is sent and the time the answer from the server is received.

• Class 1 at Server Location

  This is the ELAPSED TIME field under the APPLICATION TIMES (CLASS 1) column of the Accounting reports and traces for the server location. It represents the class 1 elapsed time from creation to termination of the DBAT.

• Class 2 at Server Location

  This is the ELAPSED TIME field under the DB2 TIMES (CLASS 2) column of the Accounting reports and traces for the server location. It represents the elapsed time to process the SQL requests and the commits at the server.

• Class 3 at Server Location

  This is the ELAPSED TIME for the total of the class 3 suspensions in the Accounting reports and traces for the server location. It represents the time the DBAT was suspended while waiting for various system events such as locking, I/O, and other requests.

• Class 3 at Requester Location

  This is the ELAPSED TIME column for class 3 suspensions on the Accounting reports and traces for the requester location. It represents the time the allied-distributed thread was suspended while waiting for various system events such as locking, I/O, and other requests.

• Class 2 at Requester Location

  This is the ELAPSED TIME field under the DB2 TIMES (CLASS 2) column of the Accounting reports and traces for the requester location. It represents the elapsed time between the application passing the SQL statement to the local (requester) Db2 system and back again. This is the time spent in DB2.

• Class 1 at Requester Location

  This is the ELAPSED TIME field under the APPLICATION TIMES (CLASS 1) column of the Accounting reports and traces for the requester location. It represents the elapsed time from creation to termination of the allied-distributed thread.