This document provides guidance on diagnosing and addressing CSM storage issues in z/OS. It describes CSM and how it manages storage, symptoms of CSM storage problems like error messages and abends, how to gather diagnostic information like dumps and traces, common causes like insufficient CSM storage parameters, and recommendations such as increasing IVTPRM00 values and CSA allocation.

1. CSM STORAGE DEBUG
By David Himmel
IBM z/OS Comm Server
Level 2

2. Purpose: Steps to approach a CSM
storage problem.
l This presentation is designed to provide
diagnostic guidance for CSM storage usage
issues.

3. Intro and Overview
l Communication Storage Manager (CSM) allows
VTAM and other applications to use the same buffer
in order to reduce data movement in the system.
l CSM interfaces with the host operating system
(MVS/ESA) to provide the storage buffer.
l CSM is used by various VTAM and TCP/IP
components.

4. External Symptoms
l CSM storage problems are indicated mostly
by IVT5506I IVTSMCEX STORAGE
ALLOCATION FAILED messages.
l Various CSM IVTxxxxI messages indicating
a CSM ECSA or CSM FIXED shortage

5. CSM Messages continued
l IVT5560I CSM ECSA STORAGE LIMIT
EXCEEDED
l IVT5561I CSM FIXED STORAGE LIMIT
EXCEEDED
l IVT5562I CSM ECSA STORAGE AT
CRITICAL LEVEL
l IVT5563I CSM FIXED STORAGE AT
CRITICAL LEVEL

6. Other External Symptoms
l CSM storage problems may also be accompanied by
other symptoms such as:
l IST564I STORAGE UNAVAILABLE: COMMON
AREA
l IST154I EXPANSION FAILED FOR IO BUFFER
POOL
l IST154I EXPANSION FAILED FOR TI BUFFER
POOL
l TCP ABEND4C5
l ABEND878

7. Obtain a Dump for Debug
l If a dump is not generated due to the nature
of the error, please obtain a dump using the
VTAM CSDUMP command for diagnosis.
l Please refer to the following YouTube video
for information on using the CSDUMP
command:
l http://www.youtube.com/watch?v=jrnho6aAl7U

8. Additional Documentation
l Obtain a VTAM Display of CSM:
l D net,CSM,OWNERID=ALL to determine
how much storage is being used and by what
job / ASID.
l If the CSM display indicates the TCP/IP ASID
owns the storage not being freed, then
include the TCP/IP ASID in the CSDUMP
command.

9. Additional CSM Displays
l Please refer to the SNA Commserver
Operations manual for detail on displays
l D net,CSMUSE
l NOTE: Please add the OWNERID=ALL
parameter on the first issue to determine
which ASID is the biggest user.

10. Dataspace Storage
l If the CSM display output indicates the CSM
storage growth is in one of the CSM
dataspace pools, dump the dataspace
named in the display output in addition to the
dump of VTAM and TCP.

11. Dump the dataspace storage…
l Command to dump CSM dataspace:
DUMP COMM=(CSM dataspace dump)
R xx,jobname=(net),DSPNAME=(1.dddddddd),
STOR=(00000000,7FFFFFFF),sdata=(nuc,csa,rgn,ls
qa,sqa,trt)

12. Dataspace dump continued
l If the DISPLAY CSM output indicates TCP/IP
owns the storage that is not getting freed,
also dump the TCP/IP dataspace
l r xx,sdata=(csa,sqa,rgn,trt,nuc),jobname=(tcpip),cont
r yy,dspname=(1.*CSM,'tcpip'.*)

13. Dumps and Traces
l For a full global list of documentation to
gather for CSM storage problems, refer to
IBM Tech note:
l www-01.ibm.com/support/docview.wss?uid=swg21308302

14. Common causes
l Fixing CSM storage shortages may be as
easy as increasing the amount of CSM
storage available
l VTPRM00 sets parameters for the
Communication Storage Manager (CSM).
IVTPRM00 is read during CSM initialization.

15. IVTPRM00 Continued
l The IVTPRM00 parameters can be changed
without a re-IPL by issuing the VTAM
MODIFY CSM command.
l The default values for IVTPRM00 are 100
MEG for both FIXED and ECSA. We suggest
that they be coded or defaulted to 100M MAX
ECSA and 100M MAX FIXED.

16. IVTPRM00 Continued
l Monitor the system for one week with DISPLAY CSM
command to determine peak usage. Adjust
IVTPRM00 MAX ECSA and MAX FIXED values to
1.5 times the highest value indicated in the DISPLAY
CSM outputs.
l ADDITIONAL NOTE:
You must adjust your IEASYSxx CSA parm to
include the additional amounts of ECSA that CSM
will be using.

17. Recommended Fix List
l Please refer to the IBM Technote mentioned
previous for a list of recommended
maintenance for known CSM issues.

18. Additional Reference Material
l For additional information on CSM storage,
please refer to the following:
l Communications Server CSM Guide
l Communications Sever SNA Diagnosis

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l Thanks for using IBM!