Use the IOSCMXR macro to obtain the address of the unit control block (UCB) common extension segment. To map the UCB common extension segment, use the UCBCMEXT DSECT of the IEFUCBOB mapping macro.
UCBLOOK and IOSCMXA macros also provide this function. However, IOSCMXR provides an alternative for passing parameters (that is, in general purpose register (GPR) 1 rather than in a parameter list). Also, UCBLOOK returns only actual, not captured, UCB addresses. For guidance about obtaining UCB information, see z/OS MVS Programming: Authorized Assembler Services Guide.
The requirements for the caller are:
Environmental factor | Requirement |
---|---|
Minimum authorization: | Problem state and any PSW key. |
Dispatchable unit mode: | Task or SRB |
Cross memory mode: | Any PASN, any HASN, any SASN |
AMODE: | 24- or 31-bit |
ASC mode: | Primary |
Interrupt status: | Enabled or disabled for I/O and external interrupts. |
Locks: | The caller may hold locks, but is not required to hold any. |
Control parameters: | None. |
The caller must pass a valid captured or actual UCB address.
The caller must pin the UCB or otherwise guarantee that the UCB will not be dynamically deleted.
The caller must supply recovery to handle any unexpected errors, such as abends.
If you input a captured UCB address, the UCB must be captured in the primary address space.
Before issuing the IOSCMXR macro, the caller does not have to place any information into any access register (AR).
Some callers depend on register contents remaining the same before and after issuing a service. If the system changes the contents of registers on which the caller depends, the caller must save them before issuing the service, and restore them after the system returns control.
None.
The standard form of the IOSCMXR macro is written as follows:
Syntax | Description |
---|---|
name | name: symbol. Begin name in column 1. |
␢ | One or more blanks must precede IOSCMXR. |
IOSCMXR | |
␢ | One or more blanks must follow IOSCMXR. |
MF=(S) | Default: S |
The parameters are explained as follows:
None.
None.