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       pmlogreduce - temporal reduction of Performance Co-Pilot archives


       $PCP_BINADM_DIR/pmlogreduce  [-z]  [-A align] [-S starttime] [-s samples] [-T endtime] [-t
       interval] [-v volsamples] [-Z timezone] input output


       pmlogreduce reads one Performance Co-Pilot (PCP) archive identified by input (this must be
       a  PCP  archive  created by pmlogger(1), pmlogextract(1) or pmlogreduce(1)), and creates a
       temporally reduced PCP archive in output.  The data  reduction  involves  statistical  and
       temporal reduction of samples with an output sampling interval defined by the -t option in
       the output archive (independent of the sampling intervals in the input  archive),  and  is
       further controlled by other command line arguments.

       For  some metrics, temporal data reduction is not going to be helpful, so for metrics with
       types PM_TYPE_AGGREGATE or PM_TYPE_EVENT, a warning is issued if these metrics  are  found
       in input and they will be skipped and not appear in the output archive.


       The command line options for pmlogreduce are as follows:

       -A align
              Specify a ``natural'' alignment of the output sample times; refer to PCPIntro(1).

       -S starttime
              Define  the start of a time window to restrict the samples retrieved from the input
              archive; refer to PCPIntro(1).

       -s samples
              The argument samples defines the number of samples to be  written  to  output.   If
              samples  is  0 or -s is not specified, pmlogreduce will sample until the end of the
              PCP archive, or the end of the time window as  specified  by  -T,  whichever  comes
              first.  The -s option will override the -T option if it occurs sooner.

       -T endtime
              Define  the termination of a time window to restrict the samples retrieved from the
              input archive; refer to PCPIntro(1).

       -v volsamples
              The output archive is potentially a multi-volume data set, and the -v option causes
              pmlogreduce to start a new volume after volsamples log records have been written to
              the output archive.

              Independent of any -v option, each volume of an archive is limited to no more  than
              2^31  bytes,  so pmlogreduce will automatically create a new volume for the archive
              before this limit is reached.

       -t interval
              Consecutive samples in the output archive will appear with a time delta defined  by
              interval;  refer  to  PCPIntro(1).  Note the default value is 600 (seconds, i.e. 10

       -Z timezone
              Use timezone when displaying the date and time,  or  interpreting  the  -S  and  -T
              options.   Timezone is in the format of the environment variable TZ as described in

       -z     Use the local timezone of the host from the input archive when displaying the  date
              and  time,  or interpreting the -S and -T options.  The default is to initially use
              the timezone of the local host.


       The statistical and temporal reduction follows the following rules:

       1.  Consecutive records from input are read without interpolation, and at most one  output
           record  is  written  for  each  interval,  summarizing  the performance data over that

       2.  If the semantics of a metric indicates it is instantaneous  or  discrete  then  output
           value  is  computed  as  the  arithmetic  mean  of the observations (if any) over each

       3.  If  the  semantics  of  a  metric  indicates  it  is  a  counter  then  the  following
           transformations are applied:
           a)  Metrics with 32-bit precision are promoted to 64-bit precision.
           b)  Any counter wrap (overflow) is noted, and appropriate adjustment made in the value
               of the metric over each interval.  This will be correct in the case  of  a  single
               counter  wrap,  but  will  silently  underestimate in the case where more than one
               counter wrap occurs between consecutive observations in  the  input  archive,  and
               silently  overestimate  in  the  case  where  a  counter  is  reset occurs between
               consecutive observations in the  input  archive;  unfortunately  these  situations
               cannot  be detected, but are believed to be rare events for the sort of production
               monitoring environments where pmlogreduce is most likely to be deployed.

       4.  Any changes in instance domains, and indeed all metadata, is preserved.

       5.  Any ``mark'' records in the input archive (as  created  by  pmlogextract(1))  will  be
           preserved in the output archive, so periods where no data is available are maintained,
           and data interpolation will not occur across these periods when the output archive  is
           subsequently processed with PCP applications.


       For each of the input and output archives, several physical files are used.
                 metadata (metric descriptions, instance domains, etc.) for the archive log
       archive.0 initial  volume of metrics values (subsequent volumes have suffixes 1, 2, ...) -
                 for input these files may have  been  previously  compressed  with  bzip2(1)  or
                 gzip(1) and thus may have an additional .bz2 or .gz suffix.
                 temporal  index to support rapid random access to the other files in the archive


       Environment variables with the prefix PCP_ are used to parameterize the file and directory
       names used by PCP.  On each installation, the file /etc/pcp.conf contains the local values
       for these variables.  The $PCP_CONF  variable  may  be  used  to  specify  an  alternative
       configuration file, as described in pcp.conf(5).


       PCPIntro(1),   pmdumplog(1),   pmlc(1),   pmlogextract(1),  pmlogger(1),  pcp.conf(5)  and


       All error conditions detected by pmlogreduce are  reported  on  stderr  with  textual  (if
       sometimes terse) explanation.

       Should  the  input  archive be corrupted (this can happen if the pmlogger instance writing
       the archive suddenly dies), then pmlogreduce will detect and report the  position  of  the
       corruption  in the file, and any subsequent information from the input archive will not be

       If any error is detected, pmlogreduce will exit with a non-zero status.


       The preamble metrics (pmcd.pmlogger.archive,, and  pmcd.pmlogger.port),
       which  are  automatically  recorded  by  pmlogger  at the start of the archive, may not be
       present in the archive output by pmlogreduce.  These metrics are only relevant  while  the
       archive is being created, and have no significance once recording has finished.