Detail trace online data storage
The following figure shows how the trace data is collected and stored in the buffers for display by the DTRAC service.
Three kinds of buffers are used for a detail trace:
Internal buffer that is filled by the Db2 Instrumentation facility
This buffer is managed internally by and Db2 in extended CSA. You cannot specify its characteristics.
Single buffer per trace containing data allocated in BBI-SS PAS extended private area with a GETMAIN
This buffer’s default size is specified in the BBIISPxx member of the BBI-SS PAS BBPARM data set. The size can be overridden with the use of the STORAGE parameter that is specified with the ATRAC request (valid for a summary or detail trace). Entries are wrapped (default of WRAP=YES; new data overlays oldest data) unless you specify WRAP=NO with the ATRAC request. WRAP can be changed at any time by using the M line command from the Current Traces view to modify the ATRAC request.
Pool of data collection buffers that is maintained by
A pool exists for each active detail trace in the BBI-SS PAS extended private area storage. A buffer is allocated for the CREATE THREAD function for each active thread being traced, and more might be needed as the thread progresses. By default, allocates these buffers as needed. Alternatively, you can specify the size and number of these buffers with the parameters listed in the following table, which are specified in the DMRBEXxx member of the BBI-SS PAS BBPARM data set (defaults for each Db2) or in the data entry panel for the ATRAC request (see Start-DB2-Trace-Request-panel).
Parameter
Description
TRBUFF=nnn
nnn is the number of buffers to be allocated.
TRSIZE=nnnK
nnn is the size in kilobytes of each buffer. If K is not specified, the value of nnn is in bytes. nnn is rounded to a multiple of 4 KB during processing.