Measure Reference Manual

Usage Notes for All PVUs and RVUs
• If a system time change takes place during a measurement, the post processing may report
incorrect results. You should consider stopping all measurements before any system time
change takes place, for example, before using the TACL SETTIME command or the
SETSYSTEMCLOCK procedure, in order to preserve measurement interval accuracy. A time
change typically takes place at Daylight Savings Time (DST) transitions.
• Use INTERVAL only if you must examine data for specific time intervals within a measurement.
INTERVAL writes to the data file all counters in all measured CPUs for every interval specified,
thus increasing the number of I/Os performed. The smaller the INTERVAL value, the heavier
the drain on system resources (CPU, disk, memory) and the faster the data-file growth. To
conserve system resources, set the INTERVAL value to the longest interval that will provide
useful information.
Very large measurements and small interval times can cause severe performance problems.
If you experience problems, reduce the number and type of entities measured or run the
measurement without a collection interval.
Usage Note for H-Series and J-Series PVUs
In Measure H02 and later PVUs, the MEASCOM START MEASUREMENT command allows the
user to select the measurement data file size, suppress counter data records in the measurement
data file, or both.
Usage Notes for G-Series PVUs
• In Measure G11 and later PVUs, the Measure subsystem default is not to build the SQL name
journal segment unless specifically requested to do so in a START MEASUREMENT command.
To switch the default to always build the SQL name journal segment, use a DEFINE before
the START MEASSUBSYS command. For more information, see the Usage Notes for START
MEASSUBSYS (page 120).
• In Measure G09 and later PVUs, the Measure subsystem default is not to build an OSS file
pathname journal segment unless specifically requested to do so in a START MEASUREMENT
command. To switch the default to always build the OSS file pathname journal segment, use
a DEFINE before the START MEASSUBSYS command. For more information, see the Usage
Notes for START MEASSUBSYS (page 120).
Examples
• In Measure G11 and later PVUs, to build the SQL name journal segment and have it appended
to a Measure data file at measurement shutdown:
+ START MEASUREMENT MDATA, SQL
• In Measure G09 and later PVUs, to build an OSS file pathname journal segment and have it
appended to a Measure data file at measurement shutdown:
+ START MEASUREMENT MDATA, OSS
• To start a measurement immediately that writes to the data file MAY07 once each hour and
stops in eight hours:
+ START MEASUREMENT MAY07, FOR 8 HOURS, INTERVAL 1 HOUR
• To start a measurement at 12:00 on October 19, 2004, continue the measurement until 12:00
on October 26, 2004, and have the measurement write to the data file OCTDATA every six
hours:
+ START MEASUREMENT OCTDATA, FROM 19 OCT 2004, 12:00 &
& TO 26 0CT 2004, 12:00, INTERVAL 6 HOURS
126 MEASCOM Commands