Assigning buffers

You must specify the OPX destination for all traces that are being recorded to an OPn buffer for the DSN1SDMP utility to use. By specifying the OPX destination, you avoid the possibility of starting a trace to a buffer that is already assigned.

If a trace is started to an OPn buffer that has already been assigned, DSN1SDMP waits indefinitely until the trace is manually stopped. The default for MONITOR-type traces is the OPX destination (the next available OP buffer). Other trace types must be explicitly directed to OP destinations via the DEST keyword of the START TRACE command. DSN1SDMP interrogates the IFCAOPN field after the START TRACE COMMAND call to determine if the trace was started to an OP buffer.

Trace Destination: If Db2 trace data is to be written to the SDMPTRAC data set, the trace destination must be an IFI online performance (OP) buffer. OP buffer destinations are specified in the DEST keyword of START TRACE.

Start of change FL 504 Sixteen OP buffer destinations exist, OP1 to OP16. End of change

The OPX trace destination assigns the next available OP buffer. Any record destined for the exclusive internal trace table (RES) is not eligible to be evaluated. For example, if you start IFCID(0) DEST(RES), this will not execute DSN1SDMP logic and cannot be acted upon.

Trace records are written to the SDMPTRAC data set when the trace destination is an OP buffer. The instrumentation facilities component (IFC) writes trace records to the buffer and posts DSN1SDMP to read the buffer when it fills to half of the buffer size.

You can specify the buffer size on the BUFSIZE keyword of the START TRACE command. All returned records are written to SDMPTRAC.

If the number of generated trace records requires a larger buffer size than was specified, you can lose some trace records. If this happens, error message DSN2724I is issued.