.-HPRSESLM--=--NOLIMIT------.
>>-+---------------------------+-------------------------------><
'-HPRSESLM--=--+-NOLIMIT--+-'
+-sess_lim-+
'-DISABLED-'
range: |
NOLIMIT, DISABLED or 1000 - 2147483647 |
Rule: HPRSESLM is meaningful only if VTAM® provides RTP-level HPR support. At a minimum,
the NODETYPE start option must also be coded and the RTP parameter
must be specified on the HPR start option.
Use the HPRSESLM start option to limit the number of sessions
that VTAM assigns to a single
RTP connection (pipe). When the number of sessions assigned to an
RTP pipe reaches the specified
sess_lim value,
new sessions are no longer assigned to that RTP pipe until the number
of sessions falls below the specified
sess_lim value;
instead, another RTP pipe is chosen or created for the new sessions.
Limiting the number of sessions on a single RTP pipe can result in
significant performance improvement by allowing concurrent traffic
on multiple RTP pipes.
- HPRSESLM=NOLIMIT
- Specifies that VTAM should
not enforce a limit on the number of sessions assigned to an RTP pipe.
- HPRSESLM=sess_lim
- Specifies that VTAM should
limit the number of sessions assigned to an RTP pipe to the number
specified by the sess_lim value. The sess_lim value
is a decimal integer in the range 1000 - 2147483647.
- HPRSESLM=DISABLED
- Specifies that VTAM should
completely disable the HPRSESLM function to allow this level of VTAM to coexist with older releases
of VTAM. HPRSESLM=DISABLED
is meaningful only on interchange nodes (ICNs). If you specify HPRSESLM=DISABLED
on any other type of APPN node, IST1070I is displayed and HPRSESLM
is set to NOLIMIT.
If HPRSESLM is not set to DISABLED, then you can
change the value of HPRSESLM (to any valid value except DISABLED)
while VTAM is running by issuing
the MODIFY VTAMOPTS command. If HPRSESLM is set to DISABLED, then
you can only change the HPRSESLM value by stopping and restarting VTAM. Although changing HPRSESLM
does not affect any sessions that have already been assigned to an
RTP pipe, the changes to HPRSESLM take effect immediately. If you
specify HPRSESLM=NOLIMIT , then VTAM does
not enforce a session limit for all new and existing RTP pipes when
new sessions are established. If you specify HPRSESLM=
sess_lim,
then VTAM immediately begins
enforcing the specified session limit (for all new and existing RTP
pipes) when new sessions are established.
The
sess_lim value specified
for HPRSESLM does not represent an absolute session limit. The actual
number of sessions assigned to an RTP pipe can exceed the specified
sess_lim value
during normal operation.
- If multiple sessions (that are between the same two APPN nodes
and that are requesting the same class of service) are initiated at
the same time, then most or all of these sessions can be assigned
to the same RTP pipe and result in the specified sess_lim value
being exceeded. This is because of a time delay between when an RTP
pipe is assigned to a session and when the active session count for
that RTP pipe is incremented.
- Although VTAM does not
assign new sessions to an RTP pipe that has reached or exceeded the
specified sess_lim value, the APPN node
on the other end of that RTP pipe can continue to add new sessions
to that RTP pipe. The node on the other end of an RTP pipe might continue
adding new sessions in the following circumstances:
- The node on the other end of the RTP pipe is not a VTAM node and does not support the HPRSESLM
(or equivalent) function.
- The node on the other end of the RTP pipe is a VTAM running an earlier (pre-V1R10) release
of z/OS® Communications Server
and does not support the HPRSESLM function.
- The node on the other end of the RTP pipe is a VTAM running z/OS Communications
Server V1R10 or later but has specified a larger HPRSESLM value than
this VTAM. (For best results,
specify the same HPRSESLM value on all of your VTAMs.)
- The nodes on both ends of the RTP pipe are VTAMs running z/OS Communication Server V1R10
or later and have specified the same HPRSESLM value, but both nodes
are adding sessions to the same RTP pipe at approximately the same
time.
- The HPRSESLM start option is not enforced for RTP pipes that are
created for interchange node (ICN) sessions. ICN sessions (sessions
that traverse both APPN and subarea portions of the SNA network through
an interchange node) impose special requirements for choosing an RTP
pipe that has an ICN as one or both of the endpoints. In some cases,
the ICN and the partner RTP node must both choose the RTP pipe that
will be used for an ICN session, but they must choose it at different
times. If these two nodes do not choose the same RTP pipe for the
ICN session, then the ICN session fails with sense code 0897000A when
the BIND arrives at the ICN over the wrong RTP pipe. To prevent this
type of problem from occurring because the two nodes involved have
different sess_lim values specified, the
HPRSESLM start option is not enforced for RTP pipes created for ICN
sessions.
Rule: Except
when HPRSESLM=DISABLED is specified, VTAM ICNs
running z/OS Communications
Server V1R10 or later always separate ICN session onto their own RTP
pipes by using a unique network connection endpoint (NCE) when creating
RTP pipes for ICN sessions. This unique ICN NCE prevents pure APPN
(non-ICN) sessions from sharing the same RTP pipe as ICN sessions.
In a typical mixed APPN and subarea network, there are generally many
more pure APPN sessions than ICN sessions. Although VTAM does not enforce the HPRSESLM start option
for ICN sessions, separating ICN sessions onto their own RTP pipes
prevents ICN sessions from overloading the RTP pipes that were created
for pure APPN sessions and minimizes the possibility of placing too
much session traffic on RTP pipes that were created for ICN sessions.