NAME

       pmGetArchiveLabel - fetch the label record from a set of performance metrics archives

C SYNOPSIS

       #include <pcp/pmapi.h>

       int pmGetArchiveLabel(pmLogLabel *lp);

       cc ... -lpcp

DESCRIPTION

       Within the framework of the Performance Co-Pilot (PCP), archives of performance metrics values may be ac‐
       cumulated and saved using the program pmlogger(1) and the LOGIMPORT(3) programming interface.

       The  routines pmGetArchiveLabel may be used to fetch the label record from a set of archives that has al‐
       ready been opened using pmNewContext(3), or pmDupContext(3), and thereby associated with the current Per‐
       formance Metrics Application Programming Interface (PMAPI) context.

       The result returned via the pointer lp is a structure that must be pre-allocated by the  caller  and  has
       the following format (defined in pmapi.h).

         typedef struct {
           int        magic;       /* PM_LOG_MAGIC | archive format version no. */
           pid_t      pid;         /* PID of logger */
           struct timespec start;  /* start of this archive */
           char       hostname[PM_MAX_HOSTNAMELEN];   /* collection host full name */
           char       timezone[PM_MAX_TIMEZONELEN];   /* generic, squashed $TZ */
           char       zoneinfo[PM_MAX_ZONEINFOLEN];   /* local platform $TZ */
         } pmLogLabel;

       pmGetArchiveLabel  can  be  used with either version 2 or version 3 archives, however some mapping may be
       required with the older version 2 archives, e.g. the start time only has microsecond resolution  and  the
       zoneinfo field is not present.  For detailed information about the archive on-disk format, refer to LOGA‐
       RCHIVE(5).

       For  an application using pmGetArchiveLabel, the most useful information from the archive label is likely
       to be in the fields start, hostname, timezone, and zoneinfo.

       The zoneinfo field contains the most detailed timezone information  available,  and  should  be  used  if
       present  (non-zero  length string).  It will only not be present in the case of version 2 archives - this
       is a new field added as part of the version 3 format.  The timezone field will always be present, however
       it is the 'squashed' timezone value and in certain situations is not the most accurate timezone.

       For older applications using pmGetArchiveLabel, the most useful information from  the  archive  label  is
       likely  to  be in the fields ll_start, ll_hostname or ll_tz.  Note that the size of the ll_hostname field
       is PM_LOG_MAXHOSTLEN (64 bytes) which is less than MAXHOSTNAMELEN (see gethostbyname(3))  on  some  plat‐
       forms.  These semantics are necessary to retain backwards compatibility with the PCP archive file format.

       pmGetArchiveLabel return zero for success.

COMPATIBILITY

       Prior to PCP 7.0 and libpcp.so.4 the pmLogLabel structure was somewhat different.  To support PMAPI tran‐
       sition, the old interface and semantics can be used if applications are linked with libpcp.so.3 or recom‐
       piled with -DPMAPI_VERSION=2.

       For a time in PCP 6.x there was a routine with the same semantics as the current pmGetArchiveLabel called
       pmGetHighResArchiveLabel  and a structure with same definition as pmLogLabel called pmHighResLogLabel al‐
       though these are now deprecated and compile-time  support  for  pmGetHighResArchiveLabel  and  pmHighRes‐
       LogLabel will be removed in a future release.

DIAGNOSTICS

       PM_ERR_NOCONTEXT
              the current PMAPI context is either invalid, or not associated with a set of archives

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).
       Values for these variables may be obtained programmatically using the pmGetConfig(3) function.

SEE ALSO

       pmlogger(1),  LOGIMPORT(3),  PMAPI(3),  pmDupContext(3),  pmGetConfig(3), pmNewContext(3), LOGARCHIVE(5),
       pcp.conf(5) and pcp.env(5).

Performance Co-Pilot                                   PCP                                  PMGETARCHIVELABEL(3)