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pmtrimnamespace(3)

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 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

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

DIAGNOSTICS

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

   PM_ERR_NOCONTEXT
          the current PMAPI context is invalid



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