What are OMEGAMON for DB2 recommendations for preventing DSNW133I?

Resolving The Problem

DB2 issues message DSNW133I when the IFI OPx buffer is filled and more data is being added to it. This occurs when DB2 produces more trace data than the Near Term History (NTH) collector can process before the buffer is full. To reduce the likelihood of these messages the NTH configuration should be reviewed.

Dataset rhilev.RKD2PAR contains members beginning with (COPTxxxx) where xxxx is the DB2 subsystem name. This is where the NTH Collector start up (configuration) parameters are specified for a given DB2 subsystem.

1. Increase the buffer size. BUFSIZE(1024) is the default and may be too small for high volume production systems. The recommended value for OMEGAMON NTH collection is BUFSIZE(2048). BUFSIZE(2048) was determined to be a good starting point. You are free to try different values and measure the results.

Refer to the DB2 manuals for limitations to the IFI buffer size.

2. Lower the number of IFCIDS that will be generated and written to the OPx.

SCAN(NO) Use this setting to not collect SCAN data; IFCIDS 15,16,17,18.
SORT(NO) Use this setting to not collect SORT data: IFCIDS 95,96
DYNAMICSQL(NO) Use this setting to not collect SQL text from dynamic SQL statements: IFCIDS 22,63.

NEGSQL(NO) Use this setting to not collect return codes on SQL events: IFCIDS 58, 59, 60, 61, 62, 64, 65, 66, 233. If NTH is not collected to sequential files, there is no reason to collect this data. This data is not externalized by the real time product. The data can be externalized by batch reporting if collected to sequential.

The collection of Scan, Sort, Dynamic SQL and NEGSQL results in a high volume of trace data generated by the DB2 subsystem. This increases CPU utilization as well as exposing the application to DSNW133I messages.

3. Insure that the OMPE collector task is running at the same or higher service level as the DB2 subsystems being monitored.

4. Experiment with the POSTPCT value. By default this is set to POSTPCT(70). This causes DB2 to alert the NTH collector when the OP buffers are 70% full, thus triggering a read of the buffer. Try lowering this value to force a read of the buffer more frequently.

The above parameters can be found in the historical reporting guide. Ensure that the above parameters are set and the OMEGAMON for DB2 started task is restarted to begin using the changed parameters.

These parameters should be changed using ICAT or PARMGEN. Failure to use ICAT or PARMGEN to record and update the parm library may result in changes being reversed the next time the libraries are generated.