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