Using the VARY ACT,UPDATE technique

You can use the VARY ACT,UPDATE technique to dynamically change certain operand values on definition statements without deactivating the major node. Only the resources that you are changing must be inactive.

To change the values, edit the existing definitions in the VTAMLST file and then issue a VARY ACT,UPDATE=ALL command.

Some VTAM-only operands can be changed, depending on the state of the resource. All other operands can be changed only by deleting the resource and adding the resource. For more information about which operands support dynamic change, see the z/OS Communications Server: SNA Resource Definition Reference.

To use the VARY ACT,UPDATE technique for dynamic reconfiguration, change the VTAMLST source file for a major node and issue a VARY ACT,UPDATE=IMPLICIT|ADD|ALL command. The command causes VTAM® to update the actual configuration to match the new definition in the VTAMLST source file. The major node can be active for ADD or ALL. Only the individual resources being added, deleted, or moved must be inactive.

Restrictions for changing PU and LU resources: When using the VARY ACT,UPDATE=ALL command to dynamically change PU and LU resources, the following additional restrictions apply:

The PUTYPE value cannot be changed. Also, you cannot add SDDLU support to a PU.
You can convert an APPN PU to a LEN PU, or a LEN PU to an APPN PU, by changing the value of the CONNTYPE operand. However, you cannot convert an APPN PU to a LEN PU if one of the following is true:
- You coded the same NETID/CPNAME value on multiple PUs.
- You coded an ADJCP definition statement for a PU to represent a partner CP and you coded the same NETID/CPNAME value on that PU.

Restrictions for changing Enterprise Extender resources: When using the VARY ACT,UPDATE=ALL command to dynamically change Enterprise Extender resources, the following additional restrictions apply:

Changes to Enterprise Extender groups require the deactivation of the group and all subordinate resources within the group. This is done by using the VARY INACT,ID=groupname command.
Changes to port connection network values require the deactivation of the group identified by the VNGROUP operand.

Restrictions for changing model CDRSCs: When using the VARY ACT,UPDATE=ALL command to dynamically change model CDRSCs in a CDRSC major node, the following additional restrictions apply:

Existing clone CDRSCs are unaffected by changes to the model CDRSC.
A model CDRSC cannot be deleted while it has clone CDRSCs.
A conventional CDRSC cannot be added when there is a clone CDRSC of the same name. First, use the VARY INACT,DELETE=YES command to remove the clone CDRSC and then add the conventional CDRSC using the VARY ACT,UPDATE=ALL command.
V ACT,UPDATE=ALL cannot be used to delete clone CDRSCs.

Restrictions for changing QDIO TRLE definitions: Stop all TCPIP devices that are using the TRLE and 2 minutes must pass before the QDIO TRLE can be updated.

Restrictions for changing applications: When using the VARY ACT,UPDATE=ALL command to dynamically change applications in an application major node, the following additional restrictions apply:

An application cannot be added when there is a clone application of the same name. First, initiate close processing for the clone application. This causes it to be deleted. Then add the application using VARY ACT,UPDATE=ALL.
An application cannot be added to the major node unless it can be added to the host name space as a resource or a shadow resource.
The VARY ACT,UPDATE=ALL command cannot be used to delete clone applications.
A model application cannot be deleted if any clone application created using the model exists.

VARY ACT,UPDATE=IMPLICIT (the default) has the same effect as implicit dynamic reconfiguration. For more information about implicit dynamic reconfiguration, see Implicit dynamic reconfiguration. For more information about the VARY ACT command, see z/OS Communications Server: SNA Operation.

With VARY ACT,UPDATE=ADD|ALL, dynamic reconfiguration changes stay in effect regardless of VTAM or NCP recycles (halt and restart) and upon takeover of an NCP. You do not need to redrive dynamic reconfiguration changes with VARY DRDS or MODIFY DR commands. It is recommended that you do not make changes to VTAMLST files during a VTAM or NCP recycle. Instead, make the changes dynamically while VTAM and NCP are running. To prepare for takeover of an NCP, distribute the new VTAMLST file to the backup host and issue the same VARY ACT,UPDATE=ADD|ALL command that you issued at the primary host.

With VARY ACT,UPDATE=ADD|ALL, you can delay the NCP generation for a longer time than you can with other methods of dynamic reconfiguration. The changes you have made in VTAMLST definition files cause more network flows between VTAM and NCP on a recycle, but you need not regenerate the NCP until performance during recycles becomes unacceptably slow. Regenerating and reloading the NCP eliminates the extra flows.

If you use the NCP/EP definition facility (NDF) to generate some definitions, make your changes to the NDF source input, run that source through NDF, and place the resulting NEWDEFN file into a VTAMLST member. Save the load module for future use. If you update the NEWDEFN file directly, your changes are lost the next time NDF is run.

Sifting of operands does take place on subordinate resources that have been added or moved by the VARY ACT,UPDATE method of dynamic reconfiguration.

Network management programs that rely on VTAMLST definitions for the network configuration have current information available to them about the configuration.

Notes: If you use the VARY ACT, the UPDATE=ALL command might override the following commands:

The VARY LOGON command to establish an automatic logon specification that is not coded on the LOGAPPL operand of a definition statement
The VARY NOLOGON command to delete an automatic logon specification that is coded on the LOGAPPL operand of a definition statement
The MODIFY DEFAULTS, DLOGMOD command to change the value of the DLOGMOD operand of a definition statement
The MODIFY TABLE command to change VTAM table associations

For example, the LOGAPPL operand in the VTAMLST definition overrides the VARY LOGON and VARY NOLOGON commands. Even if no LOGAPPL is coded in the VTAMLST definition, a null value for LOGAPPL overrides the VARY LOGON value. To avoid having the VARY LOGON command overridden, code the LOGAPPL definition statement with the required value. To avoid having the VARY NOLOGON command overridden, delete the LOGAPPL operand from the definition statement.