pmTrimNameSpace(3) — Linux manual page


PMTRIMNAMESPACE(3)        Library Functions Manual        PMTRIMNAMESPACE(3)

NAME         top

       pmTrimNameSpace - prune a performance metrics name space

C SYNOPSIS         top

       #include <pcp/pmapi.h>

       int pmTrimNameSpace(void);

       cc ... -lpcp

DESCRIPTION         top

       In some (rare) cases it is helpful to prune the Performance Metrics
       Name Space (PMNS) to match the available metrics.

       The default PMNS that is accessible to a Performance Metrics
       Application Programming Interface (PMAPI) client is provided by the
       current PMAPI context:

       ·  for a PMAPI context of type PM_CONTEXT_HOST the PMNS is provided
          by pmcd(1) on the associated host and no pruning is required

       ·  for a PMAPI context of type PM_CONTEXT_ARCHIVE the PMNS is stored
          within the associated Performance Co-Pilot (PCP) archive log and
          no pruning is required

       ·  for a PMAPI context of type PM_CONTEXT_LOCAL at the first PMAPI
          call requiring access to the PMNS it is loaded from the default
          local location $PCP_VAR_DIR/pmns/root (or $PMNS_DEFAULT) and no
          pruning is required.

       If the default PMNS is in effect then calling pmTrimNameSpace is a
       no-op and returns zero with no change to the PMNS.

       PMAPI clients also have the option of over-riding the default PMNS by
       loading a local PMNS from a file (see PMNS(5) for the format) by
       calling pmLoadASCIINameSpace(3) or pmLoadNameSpace(3) and this is
       when some PMNS pruning may be useful.

       If a local PMNS is in effect when pmTrimNameSpace is called then the
       first action is to restore the PMNS to the state as of the completion
       of the last pmLoadASCIINameSpace(3) or pmLoadNameSpace(3), so that
       the effects of consecutive calls to pmTrimNameSpace are not additive.

       The subsequent actions of pmTrimNameSpace depend on the type of the
       current PMAPI context.

       ·  For a context of type PM_CONTEXT_ARCHIVE the local PMNS is trimmed
          to exclude metrics for which no description can be found in the
          PCP archive log.  The PMNS is further trimmed to remove empty
          subtrees that do not contain any performance metric.  Since PCP
          archives usually contain some subset of all metrics named in a
          PMNS, pmTrimNameSpace effectively prunes the application's PMNS to
          contain only the names of the metrics in the archive.

       ·  For a context of type PM_CONTEXT_HOST or PM_CONTEXT_LOCAL no
          further action is required.

       On success, pmTrimNameSpace returns zero.

SEE ALSO         top

       pmlogger(1), PMAPI(3), pmLoadASCIINameSpace(3), pmLoadNameSpace(3),
       pmNewContext(3) and PMNS(5).

DIAGNOSTICS         top

              there has been some earlier problem with establishing the
              relevant PMNS

              the current PMAPI context is invalid

COLOPHON         top

       This page is part of the PCP (Performance Co-Pilot) project.
       Information about the project can be found at ⟨⟩.
       If you have a bug report for this manual page, send it to  This page was obtained from the project's upstream
       Git repository ⟨⟩ on
       2020-08-13.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-08-11.)  If you discover any
       rendering problems in this HTML version of the page, or you believe
       there is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

Performance Co-Pilot                 PCP                  PMTRIMNAMESPACE(3)

Pages that refer to this page: pmfetcharchive(3)pmFetchArchive(3)pmgetpmnslocation(3)pmGetPMNSLocation(3)pmloadasciinamespace(3)pmLoadASCIINameSpace(3)pmloadnamespace(3)pmLoadNameSpace(3)