To support your tape management system's need to coordinate complex vaulting requirements with data set allocation in system-managed environments, you can use a pre-ACS routine exit to set values for read-only variables, which SMS then uses as input to ACS routines. This support is useful when the choice of a storage group needs to be influenced by the data set's vaulting requirements. For example, you might use this support when excluding data from redirection under tape mount management or directing data to a specific system-managed library.

The four read-only variables used to support tape management system-driven tape allocations are:

&MSPDEST

used to specify a destination, in data set name format. This format lets you specify a sequence of destinations to be identified, where each qualifier is a specific destination. For example, a data set vaulted first at location OUTD and then sent to OLTS could have an MSPDEST of 'OUTD.OLTS'. The actual values depend on the support provided by your tape management system.

&MSPARM

used to specify any additional information related to a system-driven tape management allocation. This is a variable length field, and its value is specified through an external exit.

&MSPOLICY

used to specify a management policy related to a system-driven tape management allocation. This is an 8 character field, and its value is specified through an external exit.

&MSPOOL

used to specify a tape pool name associated with the data set being allocated. In a system-managed tape environment with scratch pool support, this variable might be used to specify a default storage group, where the tape storage group is equivalent to the tape pool specified in the variable.

DFSMSrmm allows you to move your pooling decisions to the SMS ACS routines so that you can assign a scratch pool based on ACS input variables. A scratch pool selected in this way equates to a storage group and includes all assigned volumes in the DFSMSrmm control data set. DFSMSrmm passes scratch pooling decisions using the pre-ACS interface in the MSPOOL variable so that it can be the base for assigning a storage group. For non-system-managed tapes, DFSMSrmm also calls the management class and storage group ACS routines so that a storage group can be assigned for use as a scratch pool name.

You can assign a storage group using the DFSMSrmm RMMPOOL environment call. DFSMSrmm uses the assigned storage group as the pool name to validate that a mounted scratch volume is from the requested pool.

DFSMSrmm also allows you to move your VRS policy assignments to the SMS routines so that you can use any of the existing ACS input variables as the base for assigning a management class. You can assign a VRS policy by name to a system-managed or non-system-managed tape data set, and DFSMSrmm uses this management class name to identify the VRS policy. DFSMSrmm passes VRS management value decisions using the pre-ACS interface in the MSPOLICY variable so that it can be the base for management class assignments. DFSMSrmm also calls ACS routines for assigning a management class to non-system-managed tapes.

When DFSMSrmm calls ACS routines for a management class or storage group name, the &ACSENVIR variable is set to RMMVRS for the required management class and RMMPOOL for the required storage group. When RMM calls the ACS routines with the &ACSENVIR variable set to either RMMPOOL or RMMVRS, &STORCLAS is set to USERMM.

See z/OS DFSMSrmm Managing and Using Removable Media and z/OS DFSMSrmm Implementation and Customization Guide for further information on the SMS pre-ACS interface and the updates to the ACS input variables.