Use the IOSUPFR macro to obtain the address of the UCB prefix extension segment. To map the UCB prefix extension segment, use the IOSDUPFX mapping macro.
UCBLOOK and IOSUPFA macros also provide this function. However, IOSUPFR provides an alternative for passing parameters (that is, in general purpose register (GPR) 1 rather than in a parameter list). 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.
None.
Before issuing the IOSUPFR 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 IOSUPFR macro is written as follows:
| Syntax | Description |
|---|---|
| name | name: symbol. Begin name in column 1. |
| ␢ | One or more blanks must precede IOSUPFR. |
| IOSUPFR | |
| ␢ | One or more blanks must follow IOSUPFR. |
| MF=(S) | Default: S |
The parameters are explained as follows:
None.
None.