NAME

       QmcMetric - container for a metric and all its values

C++ SYNOPSIS

       #include <pcp/pmc/Metric.h>

       CC ... -lpcp_pmc -lpcp

DESCRIPTION

       A QmcMetric object is a container for a single metric and all its values.

       The  QmcMetricValue structure is used to hold the instance index, values and errors of each instance.  In
       the case of a singular metric, a single QmcMetricValue object is used.

       A QmcMetric object consists of a list of QmcMetricValue  objects,  indexes  to  the  descriptors  in  the
       metric's  QmcGroup and QmcContext and flags to indicate if the instances are explicit or implicit, and if
       only active metrics are required after QmcMetric::updateIndom is called.

CONSTRUCTORS

       Metrics should be constructed through the QmcGroup::addMetric  methods  as  this  will  ensure  that  the
       references to the metric's context, descriptor and instance domain are correctly initialized.

INSTANCES

       For  metrics  with  an instance domain it is possible to add and remove any instance, and also update the
       instance list to reflect changes in a dynamic instance domain.

       bool updateIndom();
           Update the metric to include new instances.  This method will first call QmcContext::update to update
           the  instance domain.  If the active flag is set in the QmcGroup::addMetric call, only instances will
           exported by the metric, otherwise the metric will export all instances listed in the domain.

           The ordering of instances may change as a result of this call.  Instances that already  existed  will
           keep their current and previous values and errors, even if they are in a different order.

       int addInst(QString const& name);
           Add  the  instance  name  to  the  metric.   If the instance does not exist in the instance domain, a
           PMAPI(3) error will be returned.  This method ignores the  value  of  the  active  flag  set  in  the
           QmcMetric constructor.

       void removeInst(uint_t index);
           Remove the instance at position index from the metric.

SEE ALSO

       PMAPI(3), QMC(3), QMC_Context(3), QMC_Group(3), pmflush(3) and pmprintf(3).

DIAGNOSTICS

       Error  messages are generated using pmprintf(3) but are not flushed. It is the responsibility of the user
       to call pmflush(3) to output any messages.

       Additional diagnostics may be activated by adding the option pmc to the global  debugging  specification,
       as described in pmSetDebug(3).