HP NonStop G-Series - Manual (Page 46)

Configuring and Running Measurements
Measure User’s Guide — 520560-003
3 -4
Running a Measurement
Running a Measurement
1. By default, MEASCOM starts a measurement immediately after you issue the
START MEASUREMENT command and ends it when you enter the STOP
MEASUREMENT command. However, you can specify starting and ending times
for the measurement in the START MEASUREMENT command.
2. When you start a measurement, MEASCOM creates a file-handling process
(MEASFH), converts your measurement configuration to an internal format, then
passes the configuration to MEASFH.
3. MEASFH can perform additional processing on the records before passing the
configuration to MEASMON. When MEASMON receives the configuration, it
passes a copy of it to each MEASCTL process in each CPU of the system.
4. The MEASCTL processes allocate and initialize the counter records for each entity
in the measurement configuration. If an entity is already being measured, the
MEASCTL process writes the current counter values for that entity to the data file
as the initial counter values. It does not allocate and initialize new counters for the
entity. If an entity is not already being measured, its initial value is zero.
5. As the measurement continues running, the NonStop operating system, file
system, SQL executor, disk processes, communications processes, and TMF
update (bump) the counters.
6. For every entity being measured, the MEASCTL process writes counter
information to the data file at least twice: when the measurement starts and when it
ends. If you specify a collection interval in the START MEASUREMENT command,
the MEASCTL process also writes counter values to the data file at the interval you
specify.
A collection interval lets you see cumulative counter values from specified intervals
within a measurement. A collection interval is particularly useful to view data while
a measurement is running or to analyze part of a measurement. However, a
collection interval uses more system resources during a measurement. For more
information, see
Specifying a Collection Interval on page 3-6.
7. The data file is made up of variable-length records that hold information about
each resource and the value of each counter associated with each resource. The
MEASFH process creates an index on the data file with pointers to the records in it
and then sorts the index. The larger the data file, the longer it takes MEASFH to
scan the records and sort the index.
Predefined Counters
For each entity type you specify in a measurement configuration, the counters
predefined for that entity are used to collect information during the measurement.
For example, when you specify the CPU entity in a configuration, all predefined CPU
counters are activated when the measurement starts: the CPU-BUSY-TIME counter