Abbreviations
Operand |
Abbreviation |
MODIFY |
F |
Purpose
MODIFY CSM command
to update CSM storage value or to activate CSM PARMLIB member values:
The
MODIFY CSM command is used to dynamically change the amount of storage
used by the communications storage manager (CSM). It can also be used
to activate changes made to the CSM parmlib member without requiring
an IPL.
- To temporarily change the amount of storage used by CSM, issue
this command and specify the parameters you want to change on the
ECSA and FIXED operands.
- To permanently change the amount of storage used by CSM or tuning
parameters for CSM buffer pools, edit the CSM parmlib member and issue
this command without specifying any operands.
Note: Changing a parameter that decreases the specification
of a limit may not take effect immediately. Reducing the usage of
the resource to comply to the new limit may require users to free
buffers to contract a storage pool's size. This type of change could
also result in a CSM constraint condition being indicated to users
that are monitoring CSM resource usage.
For more information
about the CSM parmlib member, see the z/OS Communications Server: New Function Summary.
MODIFY CSM command to activate
or deactivate CSM Buffer Monitoring or request the dynamic CSM Buffer
Monitoring:
Using the Modify CSM command, the operator
can start or stop dynamic CSM buffer monitoring. For more information
about CSM Monitoring, see z/OS Communications Server: New Function Summary.
Operands
- procname
- The procedure name for the command. If procname in
the START command was specified as startname.ident,
where startname is the VTAM® start procedure and ident is
the optional identifier, either startname.ident or ident
can be specified for procname.
If procname in the START command was startname,
startname must be specified for procname.
- ECSA=maxecsa
- Specifies the maximum number of bytes of extended common system
area (ECSA) storage to be dedicated for use by CSM. The maxecsa value
is a decimal integer; specify the value in either kilobytes (K) or
megabytes (M) ranging from 1024K-2048M.
Guideline: The maxecsa value
should be less than 90% of the ECSA available on the z/OS® system. CSM adjusts the maxecsa value
to 90% of the system ECSA value and issues message IVT5590I when the maxecsa value
is greater than 90% of the ECSA available on the system.
- FIXED=maxfix
- Specifies the maximum number of bytes of fixed storage to be dedicated
for use by CSM. maxfix is a decimal integer
and must be specified in either kilobytes (K) or megabytes (M) ranging
from 1024K to 30720M.
Guideline: CSM ECSA and CSM data
space can be requested to be fixed. z/OS ensures
the real frame that is backing the storage matches the CSM data space
type of request. For example: CSM DSPACE64 buffers are backed with
a real frame that is above the 2G line.
- MONITOR=YES
- Specifies that CSM Buffer Monitoring will be activated. It provides
the component IDs of the users of CSM buffers in CSM buffer headers.
- MONITOR=NO
- Specifies that CSM Buffer Monitoring will be deactivated.
- MONITOR=DYNAMIC
- Specifies that CSM Buffer Monitoring will be dynamically activated
and deactivated. CSM dynamically activates CSM buffer Monitoring when
CSM storage usage approaches the critical level. It will dynamically
deactivate CSM buffer monitoring when CSM storage returns to a level
slightly lower than the normal level. The default value is DYNAMIC.
Note: - It is recommended that users review their CSM usage and IVTPRM00
parmlib specifications for ECSA and fixed CSM storage. CSM uses these
values to determine the activation and deactivation points of Dynamic
CSM buffer Monitoring. See z/OS MVS Initialization and Tuning Reference for details.
- When the CSM comes up, CSM Monitor status is dynamic by default.
The operator can modify the status of CSM Monitor active, inactive,
or dynamic. This status does not change when VTAM or TCP/IP goes down or comes up. It will
stay the same until the system is re–IPL'd, or another MODIFY
command is issued.