The sections of the trace output

Trace records can be written to SMF or GTF.

Begin program-specific programming interface information. In both cases, the record contains up to four basic sections:

  • An SMF or GTF writer header section
  • A self-defining section
  • A product section
  • Zero or more data sections

The following figure shows the format of Db2 trace records.

Figure 1. General format of trace records written by Db2
Begin figure description. This figure is described in the surrounding text. End figure description.

The writer header section begins at the first byte of the record and continues for a fixed length. (The GTF writer header is longer than the SMF writer header.)

The self-defining section follows the writer header section (both GTF and SMF). The first self-defining section always points to a special data section called the product section. Among other things, the product section contains an instrumentation facility component identifier (IFCID). Descriptions of the records in the data section differ for each IFCID.

The product section also contains field QWHSNSDA, which indicates how many self-defining data sections the record contains. You can use this field to keep from trying to access data sections that do not exist. In trying to interpret the trace records, remember that the various keywords you specified when you started the trace determine whether any data is collected. If no data has been collected, field QWHSNSDA shows a data length of zero. End program-specific programming interface information.