NAME

       pmTrimNameSpace - prune a performance metrics name space

C SYNOPSIS

       #include <pcp/pmapi.h>

       int pmTrimNameSpace(void);

       cc ... -lpcp

DESCRIPTION

       In some (rare) cases it is helpful to prune the Performance Metrics Name Space (PMNS) to match the avail‐
       able 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 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 de‐
          scription can be found in the PCP archive.  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.

DIAGNOSTICS

       PM_ERR_NOPMNS
              there has been some earlier problem with establishing the relevant PMNS

       PM_ERR_NOCONTEXT
              the current PMAPI context is invalid

SEE ALSO

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

Performance Co-Pilot                                   PCP                                    PMTRIMNAMESPACE(3)