Input Parameters

Input parameters for the function routine are:

SSOB
SSIB
SSTA

SSOB Contents: MVS™ sets the following fields in the SSOB on input:

Field Name: Description
SSOBID: Identifier 'SSOB'
SSOBLEN: Length of the SSOB (SSOBHSIZ) control block
SSOBFUNC: SSI function code 78 (SSOBTALC)
SSOBSSIB: Address of the SSIB control block
SSOBRETN: Return code value set by previously invoked function routine, or zero
SSOBINDV: Address of the function-dependent area (SSTA control block)

SSIB Contents: MVS sets the following fields in the SSIB on input:

Field Name: Description
SSIBID: Identifier 'SSIB'
SSIBLEN: Length of the SSIB (SSIBSIZE)
SSIBSSNM: Name of the subsystem enabled to receive this function code

SSTA Header Contents: There is one SSTA header for each job step or dynamic allocation that requests at least one non-SMS managed, non-DUMMY, non-SUBSYStem tape device. IBM® sets the following fields on input:

Field Name

Description

SSTAID

Identifier 'SSTA'

SSTAVERS

Current SSTA version number

SSTAFLGS

Type of call, such as:

First call for this job step or dynamic allocation invocation
Call from allocation recovery
Call from tape allocation retry processing

SSTASNAM

System name

SSTAJNAM

Job name

SSTASTNM

Job step name or procedure name and job step name. If the job step is not a procedure step, SSTASTNM is an 8-byte job step name and an 8-byte reserved field. If the job step is a procedure step, SSTASTNM is an 8-byte procedure step name and an 8-byte job step name of the step that called the procedure.

SSTASTPN

Step number

SSTANDDS

Number of DDs

SSTADDAP

Pointer to the first DD array for this job step. Set to zero if no DD array entries exist.

SSTAHDRL

Length of the SSTA header

DD Array Entry: There is one DD array entry for each DD statement or dynamic allocation that requests a non-SMS managed, non-DUMMY, non-SUBSYStem tape device. IBM sets the following fields on input:

Field Name: Description
SSTADDN: DD name. Blank if other than the first DD in a concatenation
SSTAJFCP: Pointer to the JFCB for this DD section
SSTACPOS: Concatenation position. Set to 1 for the first DD in a concatenation, 2 for the second DD, etc. Set to 1 for a DD that is not part of a concatenation
SSTADDF1: DD level information, including DISP and GDG specifications
SSTADDF2: DD level information byte 2, including unit affinity indicator
SSTANDRA: Number of devices requested
SSTADRAP: Pointer to the first device request section for this DD
SSTADDAN: Pointer to the next device request section
SSTADDAL: Length of one DD array entry

Device Request Array Entry: There is one device request array entry for each device or unit requested on a non-SMS managed, non-DUMMY, non-SUBSYStem DD statement or dynamic allocation reqest. For example, UNIT=(TAPE,2) would generate two device request array entries. IBM sets the following fields on input:

Field Name

Description

SSTAVOLI

Volume serial number. Relevant only for a specific request (indicated by bit SSTASPEC in field SSTAREQT)

SSTADNDV

Half word count of the number of eligible devices. The maximum number of eligible devices that this field can contain is 65535.

Note: This field is for compatibility only. Use the SSTANDVS field for a full word count.

SSTAREQT

Device request information flags:

SSTAPRV — indicates a private request
SSTASPEC — indicates a specific request
SSTADEFR — indicates volume mounting is deferred

SSTAVUID

Volume unit ID for affinity

SSTADEVP

Pointer to the eligible device array for this DD

SSTADRAN

Pointer to the next device request array entry

SSTANDVS

Number of eligible devices.

SSTADRAL

Length of one device request array entry

The function routine can set the SSTAUDFR and SSTAUPRF fields in the device request section. See Output Parameters.

Eligible Device Array Entry: There is one eligible device array entry for each device eligible for a particular DD array entry. IBM sets the following fields on input:

Field Name

Description

SSTADNUM

Device number, in EBCDIC. Example: The representation of device number 5B0 would be F0F5C2F0. You can use this number as input to EDTINFO to obtain further information about the device, such as its generic device type and any esoteric service groups of which this device is a part. (See z/OS MVS Programming: Assembler Services Reference ABE-HSP, GC28-1910, for additional information about EDTINFO.)

SSTAIBMM

Following are the eligibility bits that the system sets. (Unless otherwise specified, the IBM eligibility bits apply to both dedicated and automatically switchable devices.)

Field Name

Description

SSTADSK

This device is skipped for this request

SSTADMND

This device is demanded by this request. (A request is a demand request when the UNIT parameter contains a specific device number, for example, UNIT=237.)

SSTAONUN

The device is online and unallocated

SSTANAFH

This automatically switchable device is not assigned to another system

SSTASPCM

The volume mounted on this device is the one requested

SSTAACL1

Either no automatic cartridge loader (ACL) is installed and this is a specific request, or the ACL is active and the request is nonspecific (public or private)

SSTAACL2

The installed ACL is inactive

SSTAACL3

Either the ACL is active and this is a specific request, or no ACL is installed and this is a nonspecific request (public or private) request

SSTAVOLM

One of the following conditions can occur:

A volume is not mounted on this device. This is a specific volume request. The device is automatically switchable and the last volume dismounted from this device is the needed volume.
A volume is mounted on this device. This is a non-specific request for a public volume and the volume currently mounted on this device is public.

SSTANVOL

A volume is not mounted on this device for one of these possible conditions:

This is a specific volume request. The device is automatically switchable and the last volume dismounted from this device is not the needed volume.
This is a non-specific request.
This device is not automatically switchable.

SSTAWVOL

A volume is mounted on this automatically switchable device, and it matches the volume needed for this specific request. However, the last volume dismounted from this device also matches.

SSTAAVOL

A volume is mounted on this device and one of the following conditions is true:

This is a specific volume request and the volume currently mounted on this device is automatically switchable and the last volume dismounted from this device is not the needed volume.
This is a specific volume request and there is a volume currently mounted on this device, but it is not the requested volume.
This is a non-specific, private request for any volume.
This is a non-specific, public request and the volume currently mounted is private.

SSTANAS

This device is not automatically switchable

The function routine can set the SSTAPREF and SSTAUSRMM fields in the eligible device array entry. See Output Parameters.