MSC section of the DFSDFxxx member

The MSC section of the DFSDFxxx member defines attributes of the MSC function, such as MSC security options, dynamic definition of MSC resources, generic support for TCPIP links, and VTAM® generic support for VTAM links.

Some of the parameters that can be specified in the MSC section of the DFSDFxxx member can also be specified in the DFSDCxxx member of the IMS PROCLIB data set. If you specify values in both the DFSDCxxx member and the DFSDFxxx member, the values that are specified in the DFSDCxxx member override the values that are specified in the DFSDFxxx member.

Parameters

The parameters of the MSC section of the DFSDFxxx member are described in the following list.

GENIMSID=

A 1- to 8-character alphanumeric shared IMS ID that identifies a TCP/IP generic resources group in an IMSplex.

The GENIMSID= parameter can be specified in either the DFSDCxxx PROCLIB member or in the MSC section of the DFSDFxxx PROCLIB member. Specifications in the DFSDCxxx PROCLIB member override specifications made in the DFSDFxxx PROCLIB member.

Each MSC-enabled IMS system in the IMSplex that participates in the TCP/IP generic resources group must specify the same shared IMS ID on the GENIMSID parameter.

The IMS Connect instance that supports TCP/IP generic resources group in the IMSplex must also specify the shared IMS ID on the GENIMSID parameter of the IMS Connect MSC configuration statement for each participating IMS system.

MSC-enabled IMS systems outside of the IMSplex connect to the IMSplex by specifying the shared IMS ID. The shared IMS ID is specified on the NAME parameter of the definition of the MSC physical link (MSPLINK) that defines a TCP/IP-type MSC physical link to the IMSplex. The IMS systems outside of the IMSplex do not need to define a MSC links to specific IMS systems in the IMSplex.

New connections to the TCP/IP generic resources group are accepted by the first IMS system to respond to the connection request when it is passed to the IMSplex by IMS Connect. After the connection has been accepted by a participating IMS system, the MSC physical link and all logical links assigned to it have affinity with that IMS system until the link is terminated.

The IMS ID must begin with an alphabetic character.

The value of GENIMSID cannot be the same as the IMS ID of any IMS system in the IMSplex or of any remote IMS system that connects to the IMSplex by using an MSC TCP/IP link.

MSCREPO=N|Y

Specifies whether MSC resources are stored in the IMSRSC repository. These MSC resources include physical links, logical links, logical link paths, and remote logical terminals. This attribute can be changed only on an IMS cold start.

This parameter is ignored if MSC dynamic resource definition is not enabled; that is, if MSCRSCS=DYN is not specified.

N

Disables MSC resources from being stored in the IMSRSC repository. N is the default value.

Y

Enables MSC resources to be stored in the IMSRSC repository, if the following items are defined:

• MODBLKS=DYN is defined in the COMMON_SERVICE_LAYER section of the DFSDFxxx member.
• MSCRSCS=DYN is defined in the MSC section of the DFSDFxxx member.
• AUTOIMPORT=AUTO or AUTOIMPORT=REPO is defined in the DYNAMIC_RESOURCES section of the DFSDFxxx member.
• AUTOEXPORT=AUTO or AUTOEXPORT=REPO is defined in the DYNAMIC_RESOURCES section of the DFSDFxxx member.

The MSC resources are automatically exported to the repository at IMS checkpoint and automatically imported into IMS from the repository at IMS cold start.

MSCRSCS=NODYN|DYN

Specifies whether MSC resources are defined dynamically by using online commands or statically by using stage-1 system definition macros. These resources include physical links, logical links, logical link paths, and remote logical terminals. This attribute can be changed only on an IMS cold start. If the value is changed for the next IMS warm or emergency restart, IMS restart terminates and abend U0168 is issued.

This parameter is ignored if MSC is not enabled in the IMS system.

NODYN

Disables the dynamic definition of MSC resources. MSCRSCS=NODYN is the default.

When MSCRSCS=NODYN is specified, resource definitions can be added, changed, or deleted only during system definition by coding the following stage-1 system definition macros:

• MSLINK
• MSNAME
• MSPLINK
• NAME

DYN

Enables dynamic definition for MSC resources. Resource definitions can be dynamically added, changed, or deleted by using online commands, including CREATE, DELETE, and UPDATE.

Changes that are made dynamically to MSC resources are not retained over a cold start of IMS unless the online definitions are exported to the IMSRSC repository or the changes were also coded in stage-1 system definition macros.

MSCSEC=()

Specifies the security options for direct and non-direct routed transactions received from an MSC link.

The MSCSEC= parameter can be specified in either the DFSDCxxx PROCLIB member or in the MSC section of the DFSDFxxx PROCLIB member. Specifications in the DFSDCxxx PROCLIB member override specifications made in the DFSDFxxx PROCLIB member.

LINKRECV=

LRDIRECT

Specifies that Link Receive routing use RACF®, the Transaction Authorization exit routine (DFSCTRN0), or both to check security for direct routed transactions. This is the default.

LRNONDR

Specifies that Link Receive routing use RACF, the Transaction Authorization exit routine (DFSCTRN0), or both to check security for non-direct routed transactions. No security checking is performed for direct routed transactions.

LRALL

Specifies that Link Receive routing use RACF, the Transaction Authorization exit routine (DFSCTRN0), or both to check security for direct and non-direct routed transactions.

LRNONE

Specifies that the IMS subsystem does not request any security checking for either type of transaction.

TRANAUTH=

CTL

Specifies that RACF security is to authorize the use of the transaction based upon the user ID of the IMS control region.

MSN

Specifies that RACF security is to authorize the use of the transaction based upon the user ID of the MSNAME.

USR

Specifies that RACF security is to authorize the use of the transaction based upon the user ID of the inputting terminal.

EXIT

Specifies that authorization is performed by the Transaction Authorization exit routine (DFSCTRN0).

CTLEXIT

Specifies that both RACF security and the Transaction Authorization exit routine (DFSCTRN0) are used to authorize the IMS control region user ID to use the transaction.

MSNEXIT

Specifies that both RACF security and the Transaction Authorization exit routine (DFSCTRN0) are used to authorize the MSNAME to use the transaction.

USREXIT

Specifies that both RACF security and the Transaction Authorization exit routine (DFSCTRN0) are used to authorize the user ID of the inputting terminal to use the transaction.

NONE

Specifies that no security authorization checking is performed.

MSCVGR=N | Y

Specifies whether MSC links use the GRSNAME or the APPLID name in an IMS VGR environment.

The MSCVGR= parameter can be specified in either the DFSDCxxx PROCLIB member or in the MSC section of the DFSDFxxx PROCLIB member. Specifications in the DFSDCxxx PROCLIB member override specifications made in the DFSDFxxx PROCLIB member.

Y

IMS attempts to use the GRSNAME first to establish the session with the remote IMS. The remote IMS must use the value of the MSPLINK NAME=nodename for the IMSplex GRSNAME.

N

The APPLID name, not the GRSNAME, is used in an IMS VGR environment. This is true also if the remote IMS uses the IMSplex nodename. This is the default.

SYSID=()

Defines one or more system identifiers (SYSIDs) as local to this IMS system. A local SYSID is used to route response messages back to this IMS system.

The SYSID= parameter is required when MSC=Y is specified in the IMS execution parameters, unless one or more logical link paths are defined in either the IMSRSC repository or in an MSNAME stage-1 system definition macro. In either of these cases, the local SYSIDs for this IMS system are established from the logical link path definitions.

Valid values are 1 - 2036. Multiple SYSIDs must be separated by commas.

SYSIDs that are specified in the DFSDFxxx member do not override SYSIDs that are defined as remote, in either the IMSRSC repository or in an MSNAME macro, and are ignored. Message DFS3664I is issued for each SYSID that is ignored.

SYSIDs must be unique within an MSC network. However, within a single IMSplex or shared-queues group, the SYSIDs can be duplicated. For example, if you have multiple back-end IMS systems in an IMSplex with shared queues that are not connected to the MSC network but process MSC messages from the shared queue, specify the same SYSID in all of the back-end IMS systems.

To store SYSIDs, IMS creates a SYSID table. In an IMSplex with shared queues, the SYSID table is sent to the other IMS systems in the IMSplex. Each IMS system in the IMSplex builds a common SYSID table. The local SYSIDs of each IMS system in the IMSplex become local to all of the other IMS systems in the IMSplex.

To conserve online storage in shared-queues environments, always use the lowest possible SYSID values. In a shared-queues environment, the size of the table in storage is determined by the number of entries in the table. The number of entries in the table is determined by the highest specified SYSID value, up to 2036. Consequently, if the highest SYSID in a shared-queues group is relatively low, the SYSID table uses less storage.

Specifying the SYSID parameter does not require a predefined logical link.