TMF Reference Manual (G06.26+)

TMFCOM Commands
HP NonStop TMF Reference Manual—522418-003
3-118
ALTER TMF
PIOBUFFER and TMPWAITTIMER Options
By using the PIOBUFFER option, you can influence when the content of a transport
buffer is sent to its designated processor by specifying the size (piobuffersize),
maximum number of LBEs allowed (maxpiosperbuffer), and transmission delay
(piodelaytimer) for the buffer. The contents of the buffer are shipped when either
the buffer is filled or the maximum number of LBEs is reached, whichever event comes
first. If neither of these events occur and the buffer contains LBEs, the buffer contents
are transmitted based on the value specified for the TMP’s piodelaytimer setting.
By altering the buffer size, you can indirectly determine the number of LBEs sent with
each transmission; however, the maximum number of allowed LBEs might not be
reached if the buffer space is exhausted first.
To determine whether performance improvements are possible on your system, you
can change the PIOBUFFER settings in small increments while measuring
performance. In some heavily loaded systems, the values specified in the following
command have generally improved throughput:
ALTER TMF, PIOBUFFER (1800, 80, 10000)
In some lightly loaded systems, the values specified in the next command have
generally improved throughput:
ALTER TMF, PIOBUFFER (1800, 8, 10000)
Typically, customers have benefitted from changing the maxpiosperbuffer value,
and leaving the piobuffersize value at 1800 and the piodelaytimer value at
10000.
The TMPWAITTIMER option controls the wait timer in the TMP process. This option
determines the duration that the TMP waits before awakening to process new
requests.
The TMPWAITTIMER setting is not specifically related to the processing of transaction
commits. Neither is the TMPWAITTIMER setting related to the writing of commit audit
records; these records are written to the audit trail when TMP processing completes,
and are not based on a timer. Instead, the TMPWAITTIMER value tells the TMP when
to awaken and process the requests in its queue. The larger this value is, the longer
the TMP waits between wake-ups.
When the TMP awakens, it processes all work in its queue. Therefore, by varying the
TMPWAITTIMER value, you can balance transaction response time against
throughput. In general, response time is better with smaller TMPWAITTIMER values
and throughput is greater with larger TMPWAITTIMER values. However, transaction
duration and mix (short versus long transactions) should play a critical part in your
decision.
Although you specify the timer value in microseconds, TMF rounds this value to the
nearest centisecond for operational purposes. Setting the TMPWAITTIMER to 10000
microseconds has improved response time and throughput for some sites. As a