IOSWITCH provides a service which callers outside the IOS address space can use to obtain physical topology information about a specific switch and its ports.
The requirements for the caller are:
Environmental factor | Requirement |
---|---|
Minimum authorization: | Problem or Supervisor state. Any PSW key. |
Dispatchable unit mode: | Task |
Cross memory mode: | Any PASN, any HASN, any SASN |
AMODE: | 31-bit |
ASC mode: | Primary |
Interrupt status: | Enabled for I/O and external interrupts. |
Locks: | No locks may be held. |
Control parameters: | Must be in the primary address space. |
None.
The invoker must not hold any locks which would prevent this service from obtaining the IOSYNCH lock. The service must not be invoked until after the IOS space-switching PC table has been established.
Before issuing the IOSWITCH macro, the caller does not have to place any information into any register unless using it in register notation for a particular parameter, or using it as a base register.
The contents of registers 14 through 1 are altered during processing.
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 IOSWITCH macro is written as follows:
Syntax | Description |
---|---|
name | name: Symbol. Begin name in column 1. |
␣ | One or more blanks must precede IOSWITCH. |
IOSWITCH | |
␣ | One or more blanks must follow IOSWITCH. |
SWITCH=switch | switch: Symbol up to 4 characters long. |
,SWITCHAREA=switcharea | switcharea: RS-type address or address in register (2) - (12). |
,SWITCHLEN=switchlen | switchlen: RS-type address or address in register (2) - (12). |
,SUBPOOL=subpool | subpool: RS-type address or address in register (2) - (12). |
,OFFLINE | |
,RETCODE=retcode | retcode: RS-type address or register (2) - (12). |
,RSNCODE=rsncode | rsncode: RS-type address or register (2) - (12). |
,PLISTVER=IMPLIED_VERSION | Default: PLISTVER=IMPLIED_VERSION |
,PLISTVER=MAX | |
,PLISTVER=1 | |
,MF=S | Default: MF=S |
,MF=(L,list addr) | list addr: RS-type address or register (1) - (12). |
,MF=(L,list addr,attr) | |
,MF=(L,list addr,0D) | |
,MF=(E,list addr) | |
,MF=(E,list addr,COMPLETE) | |
The parameters are explained as follows:
When the calling program is unauthorized, storage is obtained in the specified subpool, provided that the caller is permitted to use that subpool. Storage will be obtained in the caller’s key; however, the resulting key will be set according to the rules for the specified subpool, as documented in z/OS MVS Programming: Assembler Services Guide. Valid subpools are: 0 - 127, 131, and 132.
When the calling program is authorized, storage is obtained in key 0. Valid subpools are: 226, 227, 228, 231, 239, 241, 245, 247, and 248.
To code: Specify the RS-type address of a fullword field, or register (2)-(12).
To code: Specify the RS-type address of a fullword field, or register (2)-(12).
If you can tolerate the size change, IBM® recommends that you always specify PLISTVER=MAX on the list form of the macro. Specifying MAX ensures that the list-form parameter list is always long enough to hold all the parameters you might specify on the execute form, when both are assembled with the same level of the system. In this way, MAX ensures that the parameter list does not overwrite nearby storage.
Use MF=S to specify the standard form of the macro, which builds an inline parameter list and generates the macro invocation to transfer control to the service. MF=S is the default.
Use MF=L to specify the list form of the macro. Use the list form together with the execute form of the macro for applications that require reentrant code. The list form defines an area of storage that the execute form uses to store the parameters. Only the PLISTVER parameter may be coded with the list form of the macro.
Use MF=E to specify the execute form of the macro. Use the execute form together with the list form of the macro for applications that require reentrant code. The execute form of the macro stores the parameters into the storage area defined by the list form, and generates the macro invocation to transfer control to the service.
None.
The following table identifies the hexadecimal return and reason codes:
Hexadecimal return code | Reason codes, meaning and action |
---|---|
00 | IOSWITCH completed successfully. |
04 | Warning.
|
08 | Program error.
|
20 | System error. An unexpected error occurred. |