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NAME | C SYNOPSIS | DESCRIPTION | DIAGNOSTICS | SEE ALSO | COLOPHON |
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PMTRIMNAMESPACE(3) Library Functions Manual PMTRIMNAMESPACE(3)
pmTrimNameSpace - prune a performance metrics name space
#include <pcp/pmapi.h>
int pmTrimNameSpace(void);
cc ... -lpcp
In some (rare) cases it is helpful to prune the Performance Met‐
rics Name Space (PMNS) to match the available metrics.
The default PMNS that is accessible to a Performance Metrics Ap‐
plication Programming Interface (PMAPI) client is provided by the
current PMAPI context:
• for a PMAPI context of type PM_CONTEXT_HOST the PMNS is provid‐
ed 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 description can be
found in the PCP archive. The PMNS is further trimmed to re‐
move 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 appli‐
cation'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.
PM_ERR_NOPMNS
there has been some earlier problem with establishing the
relevant PMNS
PM_ERR_NOCONTEXT
the current PMAPI context is invalid
pmlogger(1), PMAPI(3), pmLoadASCIINameSpace(3),
pmLoadNameSpace(3), pmNewContext(3) and PMNS(5).
This page is part of the PCP (Performance Co-Pilot) project. In‐
formation about the project can be found at ⟨http://www.pcp.io/⟩.
If you have a bug report for this manual page, send it to
pcp@groups.io. This page was obtained from the project's upstream
Git repository ⟨https://github.com/performancecopilot/pcp.git⟩ on
2025-08-11. (At that time, the date of the most recent commit
that was found in the repository was 2025-08-11.) 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 man-pages@man7.org
Performance Co-Pilot PCP PMTRIMNAMESPACE(3)
Pages that refer to this page: pmfetcharchive(3), pmgetpmnslocation(3), pmloadasciinamespace(3), pmloadnamespace(3)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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