IST520I

Explanation
 This message is the first in a group of messages
that VTAM® issues in response
to a lack of storage, the abnormal termination of a VTAM program, or an RU received out of sequence.
A complete description of the message group follows.  If the reason is insufficient storage or a VTAM program abend, the following message group
is displayed.   IST520I  UNABLE TO PROCESS runame {REQ|RSP} [FROM fromnetid] [TO tonetid]
[IST531I  FROM SUBAREA = subarea, ELEMENT = element]
[IST531I  TO SUBAREA = subarea, ELEMENT = element]
 IST523I  REASON = reason

If the reason is an RU received out of sequence, the following
message group is displayed.   IST520I  UNABLE TO PROCESS runame {REQ|RSP} [FROM fromnetid] [TO tonetid]
 IST1694I REASON = SEQUENCE NUMBER ERROR
 IST314I  END

 IST520I  tonetid cannot process the request or response
unit (RU) runame. See Command and RU types in VTAM messages for a description of runame.
If runame is not in Command and RU types in VTAM messages,
it is the 3-byte network services header of an RU preceded by a 1-byte
category code.  The origin and destination of runame are
identified by either their:  Network names (fromnetid and tonetid)
as displayed in message IST520I; or
Network addresses (subarea address subarea and
element address element) as displayed in message
IST531I.

 IST531I  VTAM will not display
message IST531I if both FROM network name fromnetid and TO network
name tonetid are known to VTAM. VTAM will
display it once if one of the network names is unknown and twice if
both of the network names are unknown. If the subarea and element
addresses are unknown, VTAM issues
either 0 or *NA* in place of the address.

 IST523I  The reason in message IST523I can be any of
the following:  INSUFFICIENT STORAGE
VTAM PROGRAM ABEND

 IST1694I  VTAM will display message
IST1694I if the sequence number field in the TH of the RU is not the
sequence number that VTAM expected.

System action
 Processing continues. Because VTAM cannot process runame,
other VTAM operations might
fail.

Operator response
 Save the system log for problem determination.

System programmer response
 For REASON = INSUFFICIENT STORAGE
 Verify that the operator entered the buffer pool or CSA start
options as specified in the start procedures.
Increase storage as required. For insufficient storage errors,
you might want to redefine your buffer pool or CSA limits. If the
start option cannot be modified using the MODIFY VTAMOPTS command,
you must modify the VTAM start
options file (ATCSTRxx) and restart VTAM to use the start option.
See the z/OS Communications Server: New Function Summary to determine the storage requirements for VTAM.
See the z/OS Communications Server: SNA Resource Definition
Reference for a description of VTAM start options.
See z/OS Communications Server: SNA Operation for information about the DISPLAY BFRUSE
command, the DISPLAY STORUSE command, and the MODIFY VTAMOPTS command.
See the z/OS Communications Server: SNA Network Implementation
Guide for an explanation and description of buffer
pools and for general information on buffer pool specification and
allocation.

 For REASON = VTAM PROGRAM
ABEND  See the z/OS Communications Server: SNA Diagnosis Vol
2, FFST Dumps and the VIT for information about analyzing dumps and
about analyzing storage using the VIT analysis tool, if external trace
is active.

 For REASON = SEQUENCE NUMBER ERROR  Investigate why fromnetid sent an RU out of
sequence. If you suspect an       ongoing problem, you can deactivate
the session between fromnetid and        tonetid.
See the section on non-VTAM problems in the        z/OS Communications Server: SNA Diagnosis Vol
1, Techniques and Procedures for additional problem determination actions.

Routing code
 8

Descriptor code
 4 