ACB address space

An ACB address space is an address space in which an ACB is opened. The ACB must reside in common storage if multiple address spaces are to be used for the application program. An ACB address space has the following characteristics:

It can use the full set of VTAM® macroinstructions.
It can have more than one ACB.
It can issue VTAM macroinstructions in TCB mode (authorized path or non-authorized path), or in SRB mode.
It can be an associated address space (defined in the following) with respect to another ACB.
It can be a session address space (defined in the following).
It is the address space where certain EXLST exits are executed.
It is the only address space in which the ACB can be closed.

If the ACB address space terminates or the ACB is closed, all sessions associated with the ACB are terminated, no matter which address space each session uses.

Figure 1. Example of a multiple-address-space configuration with one multiple-address-space ACB

The diagram shows an example multiple-address-space configuration with only one multiple-address-space ACB. In this ACB address space, the ACB is opened. ACB1 is also used by other address spaces for sessions.

Note:

The ACB must reside in commonly addressable storage if VTAM requests specify that the ACBs are issued in address spaces other than that which issued the OPEN ACB (that is, if multiple address spaces are used for the application program).
One or more sessions can be associated with each session address space.

Figure 2. Example of a multiple-address-space configuration with more than one multiple-address-space ACB

The diagram shows an example multiple-address-space configuration with two multiple-address-space ACBs. In each ACB address space, the ACB is opened. ACB1 and ACB2 are also used by other address spaces for sessions.

Figure 3. Categories of VTAM macroinstructions versus the multiple-address-space functions

The diagram shows declarative macroinstructions must be in the address space of any macroinstructions that reference the control blocks. Manipulative macroinstructions must be issued in the address space of the control blocks that they reference. ACB-based and RPL-based macroinstructions can be issued from any address space except the noted situations.

Note:

See Address space used for exit routine execution for RECEIVE OPTCD=ANY considerations.
Except for RECEIVE OPTCD=ANY, CHECK must be issued in the address space used to issue the RPL-based macroinstruction.
Follows the same rules as the RPL-based macroinstruction it replaces.