Connect

The Connect service is used by a transaction scheduler to inform APPC/MVS that an address space is a subordinate address space of a particular transaction scheduler. The subordinate address space is said to be connected to that transaction scheduler. The Connect service must be issued by the same address space that issued the Identify. Connect is only required for a transaction scheduler managing subordinate address spaces.

A connection is required to provide an integrity structure for APPC/MVS. When a transaction scheduler issues an Identify, an implicit Connect is assumed. A transaction scheduler may associate or reassociate transaction programs from one subordinate address space to another. The connection allows APPC/MVS to ensure that TPs attached from one scheduler are always associated with address spaces connected with that scheduler.

A connection also enables APPC/MVS to process outbound Allocate requests from an MVS program. The base LU name of the transaction scheduler associated with the outbound allocate request is defined in the APPCPMxx parmlib member.

An address space remains connected to a particular transaction scheduler until the address space is terminated or issues an explicit Disconnect. (See Disconnect.) Memory termination causes an automatic Disconnect.

Environment

Authorization:

Supervisor state or PSW key 0-7

Dispatchable unit mode:

Task mode

Cross memory mode:

Any PASN, any HASN, any SASN

AMODE:

31-bit

ASC mode:

Primary or access register (AR)

Interrupt status:

Enabled for I/O and external interrupts

Locks:

Unlocked

Control parameters:

All parameters must be addressable by the caller and in the primary address space.

Format

Figure 1. ATBCONN - Connect Service

CALL ATBCONN (ASCB_ptr, 
              Return_code
             );

Parameters

ASCB_ptr

Supplied parameter

Type: Pointer
Char set: N/A
Length: 32 bits

Specifies the pointer to the address space control block (ASCB) of the address space being connected to the transaction scheduler.

Return_code

Returned parameter

Type: Integer
Char Set: N/A
Length: 32 bits

Connect may return one of the following decimal values in the return code parameter:

Decimal: Meaning
0: Address space successfully connected.
4: ASCB_ptr was invalid.
8: Connect was rejected, having specified an address space that already had outstanding APPC conversations or service calls, or an address space that was already connected. You might need to call Cleanup_Address_Space before trying to Connect.
32: The requested service is not supported in the caller's environment. For example, this return code will be given if the caller invokes any of the transaction scheduler services while holding a lock.
34: The requested transaction scheduler service must be invoked from a transaction scheduler address space.
44: APPC/MVS is not active.
48: APPC/MVS services failure.

Characteristics and Restrictions

The caller's home address space must be the transaction scheduler address space (that is, the same home address space that issued the Identify).
A transaction scheduler must issue Identify before it can issue a Connect.
Transaction schedulers that call the Connect service should not have any enabled unlocked task (EUT) functional recovery routines (FRRs) established. For more information about EUT FRRs, see the information on providing recovery in z/OS MVS Programming: Authorized Assembler Services Guide.