Subsystem Control Point (SCP) Management Programming Manual

Tr ac ing

Subsystem Control Point (SCP) Management Programming Manual—520619-001

B-5

Tracing to Memory

If ZTRC-DDL-TRACE-MODIF.ZCOLL has a value of ZSPI-VAL-FALSE, trace data

is written primarily to the extended data segment. The collector passively monitors the

trace and writes the data remaining in the segment to disk only when the trace is stopped

because:

•

The requester issues a TRACE command to stop the trace.

•

The number of records written to the segment is equal to ZTRC-DDL-TRACE-

MODIF.ZCNT (if ZCNT contains a positive value).

•

The memory segment is full, and ZTRC-DDL-TRACE-MODIF.ZWRAP has a value

of FALSE.

If TRACE-MODIF.ZWRAP is TRUE, old data in the segment is overwritten once the

segment is full.

The tracing process calls the trace procedure to write one record at a time to the

extended data segment, as Figure B-2

shows.

Figure B-2. A Tracing Process Writes a Record

Extended Data Segment

Record Written by Tracing Process

VST038.vsd