REQUEST=DISCARDDATA allows you to discard data within physical pages of one or more memory objects.
The requirements for the caller are:
| Environmental factor | Requirement |
|---|---|
| Minimum authorization: | Problem state and PSW key 8-15. The caller must be running in supervisor state or with PSW key 0-7 or have a PSW key that matches the storage key of the memory object to be cleared by DISCARDDATA. |
| Dispatchable unit mode: | Task or SRB |
| Cross memory mode: | Any PASN, any HASN, any SASN |
| AMODE: | 31- or 64-bit |
| ASC mode: | Primary or access register (AR) |
| Interrupt status: | Enabled for I/O and external interrupts |
| Locks: | When a local lock is held for a request (GETSTOR, SHAREMEMOBJ, DETACH, or DISCARDDATA) the lock must be for the address space specified (or defaulted) by the input ALETVALUE. |
| Control parameters: | Control parameters must be in the primary address space and can reside both below and above the bar. |
None
This macro supports multiple versions. Some keywords are unique to certain versions. See PLISTVER parameter description.
Before issuing the IARV64 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.
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.
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The REQUEST=DISCARDDATA option of the IARV64 macro is written as follows:
| Syntax | Description |
|---|---|
| name | name: symbol. Begin name in column 1. |
| ␢ | One or more blanks must precede IARV64. |
| IARV64 | |
| ␢ | One or more blanks must follow IARV64. |
| REQUEST=DISCARDDATA | |
| ,KEEPREAL=YES | Default: KEEPREAL=YES |
| ,KEEPREAL=NO | |
| ,CLEAR=YES | Default: CLEAR=YES |
| ,CLEAR=NO | |
| ,RANGLIST=ranglist | ranglist: RS-type address or address in register (2) - (12). |
| ,ALETVALUE=aletvalue | aletvalue: RS-type address or address in register (2) - (12). |
| ,ALETVALUE=0 | Default: ALETVALUE=0 |
| ,NUMRANGE=numrange | numrange: RS-type address or address in register (2) - (12). |
| ,NUMRANGE=1 | Default: NUMRANGE=1 |
| ,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=0, 1, 2, 3, 4 | |
| ,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:
For shared memory objects, the address space specified by the ALET or the default must have access to the memory object before issuing the DISCARDDATA (must have issued the IARV64 SHAREMEMOBJ prior to issuing the request).
Areas of the memory object that are PAGEFIXed, or are guard areas in the address space identified by the input ALET will not be discarded. If the DISCARDDATA service finds a PAGEFIXed, hidden, read-only, or guard area in the area to be discarded, the caller will be abnormally ended. However, any prior pages processed will have data in an indeterminate state when CLEAR=NO is used, and KEEPREAL=YES is also used or set as the default.
The caller must be in supervisor state or have PSW key 0-7 or have a PSW key that matches the storage key of the memory object to be cleared.
The address specified must be within a memory object returned by GETSTOR, GETSHARED, or GETCOMMON.
The value must always be on a physical 4 KB-page boundary.
The number of 4 KB-pages specified starting with the specified VSA must lie within a single memory object.
The length of this field is 8 bytes.
To code: Specify the RS-type address, or address in register (2)-(12), of an eight-byte pointer field.
The only supported values are 0 (primary) and 2 (home). The ALETVALUE parameter can be used only by callers running in supervisor state or with PSW key 0-7. The default is 0.
To code: Specify the RS-type address, or address in register (2)-(12), of a fullword field.
The value specified must be no greater than 16. The default is 1.
To code: Specify the RS-type address, or address in register (2)-(12), of a fullword field.
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.