NBX Manual

NBX Commands

NBX Manual—424774-001

3-51

TRACE

TRACE controls program tracing. The NBX trace is implemented via an extended data

segment (edseg) that is associated with a user-specified disk file. NBX creates trace

entries by direct memory access to the edseg. When the trace is stopped, or if NBX stops

for any reason, the Compaq NonStop system flushes all remaining information from the

edseg to the disk file.

You can control the trace file size. When the end of the trace file is reached, it wraps

around back to the beginning, overwriting the oldest record in the file. The file can wrap

repeatedly, storing the last size bytes of trace data. The combination of fast trace writes

and the wraparound storage lets you run the trace continuously to catch intermittent

problems. Simply set the trace file size to a large enough value to ensure that you have

enough time after detection of the problem to stop the trace without losing any

information.

You can format the trace file on the fly while the trace is still active, or after the trace is

stopped. Refer to Using NBXGTRED

on page 4-3 for additional information.

NBX needs to read the NBX program object file to copy tables to the trace file. If the

object file is not secured to allow read access by the NBX process, then the trace

command will be rejected with the response

Read object error

EMS event znbx-evt-trace-object is generated in this case, and also when

PARAM TRACE^FILE encounters the same error. Resecure the object file to allow read

access by NBX, then reissue the TRACE command.

Tracing will significantly affect NBX performance, slowing response time and

increasing processor load, so only use traces when necessary.

displays the current status and setting of the trace file and all parameters.

OFF

stops the trace.

RESET

resets the trace file pointers, effectively restarting the trace, but without the overhead

of stopping and starting the trace again.

TRACE ?

[OFF]

[RESET]

[ON] filename [ ,size]