HP NonStop G-Series User Manual
Page 127
Creating a Custom Measurement Application
Measure User’s Guide — 520560-003
6- 15
Reading Counter Records From a Data File
By default, both MEASREAD and MEASREAD_DIFF_ return the most recent record
for an entity. This record is written at measurement, at entity stop time, or at the last
collection interval. Both procedures have optional parameters you can use to specify a
target time for records:
•
With the MEASREAD procedure, the
nomtime
parameter specifies a target time.
Instead of returning the most recent record for an entity, MEASREAD returns the
record whose TO-TIMESTAMP field is closest to the specified target time.
The
timetol
parameter establishes a time window in which the record must
reside. The window is the interval between
nomtime
-
timetol
and
nomtime
+
timetol
. If MEASREAD does not find a record whose TO-TIMESTAMP resides
within the window, it does not return a record for that entity. If it finds more than
one record, it returns the record whose TO-TIMESTAMP is closest to
nomtime
.
If you use the
timetol
parameter, remember that some entities do not exist for an
entire measurement interval. If you use
timetol
to specify a window that is less
than the measurement interval, you might unintentionally exclude transient entity
records. For example, if you have a measurement interval of 30 seconds, a
transient entity can start and stop during the first 10 seconds of this interval. If you
specify a
timetol
of 15 seconds, you will not receive this entity record.
•
With the MEASREAD_DIFF_ procedure, the
to
^
time
and
from
^
time
parameters specify a target time window for the records. The
timetol
parameter
specifies the tolerance on either side of the time window.
Instead of returning the most recent record for an entity, MEASREAD_DIFF_
returns the records at
to
^
time
subtracted from the records at
from
^
time
. If
MEASREAD_DIFF_ does not find a record within the window, it does not return a
record for that entity. If it finds more than one record that could satisfy the
to
^
time
or
from
^
time
specification, it returns the record closest to the respective end
point (either
to
^
time
or
from
^
time
). For more information, see the
MEASREAD_DIFF_ procedure in the Measure Reference Manual.
on page 6-16 shows how to use MEASREAD to open a data file and read
the most recent records for all DISC entities into an extended segment; 65536 bytes
are allocated in the extended segment for the returned records. (In many cases, you
might need more space.)