Use this system macro to return the subchannel number, status, and (if
mounted) the mount parameters passed by the MSDAC macro, which is the mount
symbolic device address (SDA) macro. Optionally, the path
management control words and the subchannel status words will be
returned.
See MSDAC-Mount a Symbolic Device Address (SDA) for more information about the MSDAC macro.
Format
- label
- A symbolic name can be assigned to the macro statement.
- DDB
- The device data block (DDB), which can be either of the following:
- label1
- A symbol can be assigned to an area of memory that contains a DDB as
defined by the DCTDDB DSECT.
- (reg)
- A register with the address of the area of memory that contains the
DDB.
Entry Requirements
- The TPF system must be disabled for interrupts.
- The TPF system must be running with PSW key 0.
- The DDBSDA field must be set with the device address of an
input/output (I/O) address.
- The DDBX flag in the DDBFGO field must be set to 1 when the path
management control words and the subchannel status words are to be returned in
the DDB.
Return Conditions
- Control is returned to the next sequential instruction (NSI).
- Register 15 (R15) will contain one of the following return codes:
- Return Code
- Meaning
- 0
- The SDA is in use.
- 4
- The SDA is available.
- 8
- The SDA is not valid.
- R0-R14 are unchanged.
- If DDBX=1 and the return code is not 8, the path management control words
and subchannel status words are returned in the extended area of the
DDB.
- The channel path identifier (CHPID) type indicator is returned in the
DDB.
Programming Considerations
- This macro can be run only on an I-stream having affinity with the
specified SDA.
- This macro can be used only to interrogate SDAs associated with I/O
devices.
- This macro is for use in the control program (CP) only.
Examples
None.