The Question is:
When I monitor the buffered I/O rate using the OpenVMS Monitor utility, I see
buffered I/O rates of about 9000 buffered I/Os per second, but when I use
either AMDS or Availability Manager, I see values of about 900.
Which one do I believe, or how can I get an accurate figure?
The Answer is :
Using ANALYZE/SYSTEM, EXAMINE the system data cell PMS$GL_BUFIO, then
wait a known number of seconds (eg: 10), then re-examine the same cell.
Subtract the first value seen from the second, and then divide that by
the interval between the two EXAMINE commands. The result will be your
buffered I/O rate, per second.
For the system-wide direct I/O value, examine PMS$GL_DIRIO.
For alternatives, please see the sys$getrmi system service (on OpenVMS
V7.3 and later), and also consider researching the (undocumented and
unsupported) exe$getspi call.
As for the differences between MONITOR and AMDS, that would clearly
appear to be either a bug or a misinterpretation of a display, though
whether this problem is within AMDS or MONITOR or elsehwere is unclear.