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NAME

       pmlogreduce - temporal reduction of Performance Co-Pilot archives

SYNOPSIS

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

DESCRIPTION

       pmlogreduce reads one set of Performance Co-Pilot (PCP) archives identified by  input  and
       creates  a  temporally  reduced PCP archive in output.  input is a comma-separated list of
       names, each of which may be the base name of  an  archive  or  the  name  of  a  directory
       containing  one  or  more  archives.  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 archives), 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.

OPTIONS

       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
              archives; 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
              set  of  PCP  archives, 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 archives; 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
              minutes).

       -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
              environ(7).

       -z     Use the local timezone of the host from the input archives 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.

DATA REDUCTION

       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
           period.

       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
           interval.

       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 archives, and
               silently overestimate in the case where a counter reset occurs between consecutive
               observations  in  the  input  archives;  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 archives (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.

FILES

       For each of the input and output archives, several physical files are used.
       archive.meta
                 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.
       archive.index
                 temporal index to support rapid random access to the other files in the  archive
                 log.

PCP ENVIRONMENT

       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).

SEE ALSO

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

DIAGNOSTICS

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

       Should the input archives 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 archives will not be
       processed.

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

CAVEATS

       The  preamble metrics (pmcd.pmlogger.archive, pmcd.pmlogger.host, 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.