A subpool is a group of logically related storage blocks identified by a subpool number. In a request for virtual storage, a subpool number indicates the type of storage that is requested. Table 1 lists the subpools and their attributes. Be sure to read the notes at the end of the table where applicable.
See z/OS MVS Programming: Authorized Assembler Services Guide for
more information about subpools.
| Subpool dec (Hex) | Location | Fetch protection | Type | Storage built | Owner | Storage key | See notes |
|---|---|---|---|---|---|---|---|
| 0-127 (0-7F) | Private low | Yes | Pageable | Bottom-up | Task. TCB identified in note 11. |
Same as TCB key at the time of the first storage request. | 1, 6, 8, 10, 14 |
| 129 (81) | Private low | Yes | Pageable | Bottom-up | Job step. TCB whose address is in TCBJSTCB of TCB identified in note 11. |
Selectable. See Table 1. | 1, 11, 14 |
| 130 (82) | Private low | No | Pageable | Bottom-up | Job step. TCB whose address is in TCBJSTCB of TCB identified in note 11. |
Selectable. See Table 1. | 1, 11, 14 |
| 131 (83) | Private low | Yes | Pageable | Bottom-up | Job step. TCB whose address is in TCBJSTCB of TCB identified in note 11. |
Selectable. See Table 1. | 1, 6, 7, 11, 14 |
| 132 (84) | Private low | No | Pageable | Top-down | Job step. TCB whose address is in TCBJSTCB of TCB identified in note 11. |
Selectable. See Table 1. | 1, 6, 7, 11, 14 |
| 203 (CB) | Private ELSQA | No | DREF | Top-down | Task. TCB shown in Table 1. |
0 | 2, 4, 13, 15 |
| 204 (CC) | Private ELSQA | No | DREF | Top-down | Job step. TCB whose address is in TCBJSTCB of TCB shown in Table 1. |
0 | 2, 4, 13, 15 |
| 205 (CD) | Private ELSQA | No | DREF | Top-down | Address space | 0 | 2, 4, 13, 15 |
| 213 (D5) | Private ELSQA | Yes | DREF | Top-down | Task. TCB shown in Table 1. |
0 | 2, 4, 13, 16 |
| 214 (D6) | Private ELSQA | Yes | DREF | Top-down | Job step. TCB whose address is in TCBJSTCB of TCB shown in Table 1. |
0 | 2, 4, 13, 16 |
| 215 (D7) | Private ELSQA | Yes | DREF | Top-down | Address space | 0 | 2, 4, 13, 16 |
| 223 (DF) | Private ELSQA | Yes | Fixed | Top-down | Task. TCB shown in Table 1. |
0 | 2, 4, 17 |
| 224 (E0) | Private ELSQA | Yes | Fixed | Top-down | Job step. TCB whose address is in TCBJSTCB of TCB shown in Table 1. |
0 | 2, 4, 17 |
| 225 (E1) | Private ELSQA | Yes | Fixed | Top-down | Address space | 0 | 2, 4, 17 |
| 226 (E2) | Common SQA/ESQA | No | Fixed | Top-down | System | 0 | 3, 5 |
| 227 (E3) | Common CSA/ECSA | Yes | Fixed | Top-down | System | Selectable. See Table 1. | 1 |
| 228 (E4) | Common CSA/ECSA | No | Fixed | Top-down | System | Selectable. See Table 1. | 1 |
| 229 (E5) | Private high | Yes | Pageable | Top-down | Task. TCB shown in Table 1. |
Selectable. See Table 1. | 1 |
| 230 (E6) | Private high | No | Pageable | Top-down | Task. TCB shown in Table 1. |
Selectable. See Table 1. | 1 |
| 231 (E7) | Common CSA/ECSA | Yes | Pageable | Top-down | System | Selectable. See Table 1. | 1 |
| 233 (E9) | Private LSQA/ELSQA | No | Fixed | Top-down | Task. TCB shown in Table 1. |
0 | 2, 19 |
| 234 (EA) | Private LSQA/ELSQA | No | Fixed | Top-down | Job step. TCB whose address is in TCBJSTCB of TCB shown in Table 1. |
0 | 2, 20 |
| 235 (EB) | Private LSQA/ELSQA | No | Fixed | Top-down | Address space | 0 | 2, 21 |
| 236 (EC) | Private high | No | Pageable | Top-down | Task. TCB identified in note 12. |
1 | 2, 12 |
| 237 (ED) | Private high | No | Pageable | Top-down | Task. TCB identified in note 12. |
1 | 2, 12 |
| 239 (EF) | Common SQA/ESQA | Yes | Fixed | Top-down | System | 0 | 2 |
| 240 (F0) | Private low | Yes | Pageable | Bottom-up | Task. TCB identified in note 11. |
Same as TCB key at the time of the first storage request. | 1, 9, 10, 11, 14 |
| 241 (F1) | Common CSA/ECSA | No | Pageable | Top-down | System | Selectable. See Table 1. | 1 |
| 244 (F4) | Private Low | No | Pageable | Bottom-up | Job step. TCB whose address is in TCBJSTCB of TCB identified in note 11. |
Selectable. See Table 1. | 1, 14 |
| 245 (F5) | Common SQA/ESQA | No | Fixed | Top-down | System | 0 | 2 |
| 247 (F7) | Common ESQA | Yes | DREF | Top-down | System | 0 | 2, 4, 13 |
| 248 (F8) | Common ESQA | No | DREF | Top-down | System | 0 | 2, 4, 13 |
| 249 (F9) | Private high | No | Pageable | Top-down | Job step. TCB whose address is in TCBJSTCB of TCB shown in Table 1. |
Selectable. See Table 1. | 1 |
| 250 (FA) | Private low | Yes | Pageable | Top-Down | Task. TCB identified in note 11. |
Same as TCB key at the time of the first storage request. | 1, 9, 10, 11, 14 |
| 251 (FB) | Private low | Yes | Pageable | Bottom-up | Job step. TCB whose address is in TCBJSTCB of TCB shown in Table 1. |
Same as TCB key at the time of the first storage request. | 1, 10, 14 |
| 252 (FC) | Private low | No | Pageable | Bottom-up | Job step. TCB whose address is in TCBJSTCB of TCB shown in Table 1. |
0 | 1, 14 |
| 253 (FD) | Private LSQA/ELSQA | No | Fixed | Top-down | Task. TCB shown in Table 1. |
0 | 2, 18 |
| 254 (FE) | Private LSQA/ELSQA | No | Fixed | Top-down | Job step. TCB whose address is in TCBJSTCB of TCB shown in Table 1. |
0 | 2, 18 |
| 255 (FF) | Private LSQA/ELSQA | No | Fixed | Top-down | Address space. | 0 | 2, 18 |
Note:
- Virtual storage is first backed by central storage
when it is referenced or when it is page-fixed by a program using
the PGSER macro. The location of the central storage backing this
subpool depends on the value of the LOC parameter on the GETMAIN,
STORAGE, or CPOOL macro invocation used to obtain the storage. Central
storage is assigned below 16 megabytes only if one of the following
is true:
- The program obtaining the storage specified LOC=BELOW when obtaining the storage.
- The program obtaining the storage resides below 16 megabytes, specified LOC=RES either explicitly or by default, and specified a subpool supported below 16 megabytes.
- Central storage backing this subpool can be above or below 16 megabytes.
- Central storage backing this subpool resides below 16 megabytes.
- This subpool is valid only when allocating virtual storage above 16 megabytes.
- Although central storage for this subpool must be below 16 megabytes, virtual storage for this subpool may be above or below 16 megabytes.
- Subpools 0-127, 131, and 132 are the only valid subpools for unauthorized programs. A request by an unauthorized program for a subpool other than 0-127, 131, or 132 causes abnormal termination of the program.
- A program can issue a request to obtain or release
storage from subpool 131 or 132 in a storage key that does not match
the PSW key under which the program is running. However, the system
will accept the storage request only if the requesting program is
authorized in one of the following ways:
- Running in supervisor state
- Running under PSW key 0-7
- APF-authorized
- Having a PSW-key mask (PKM) that allows it to switch its PSW key to match the storage key of the storage specified. On a request to release all the storage in the subpool, the program must be able to switch its PSW key to match all the storage keys in the subpool.
- Subpool 0 requests by programs in supervisor state and PSW key 0 are translated to subpool 252 requests and assigned a storage key of 0.
- Subpool 240 and 250 requests are translated to subpool 0 requests. This permits programs running in supervisor state and PSW key 0 to acquire or free subpool 0 storage. If a program is running in supervisor state and key 0, the system translates subpool 0 storage requests to subpool 252 storage requests.
- The system assigns the storage key based on the key in the requesting task's TCB at the time of the task's first storage request, not the current key in the TCB (unless this is the task's first storage request).
- The GSPV, SHSPV, and SZERO parameters on the ATTACH or ATTACHX macro invocation used to create the currently active task determine which TCB owns the storage in this subpool. These parameters specify the subpools to be owned by the subtask being attached (GSPV) and the subpools to be shared by the attaching task and the subtask being attached (SHSPV, SZERO). If the currently active task was given ownership of the subpool, then the TCB of the currently active task owns the storage in this subpool. If the currently active task is sharing this subpool with the task that created it, then the TCB of the attaching task owns the storage in this subpool. For more information, see the descriptions of the ATTACH and ATTACHX macros in z/OS MVS Programming: Authorized Assembler Services Reference ALE-DYN and the virtual storage management topic in z/OS MVS Programming: Assembler Services Guide.
- Virtual storage is located within the scheduler work
area (SWA). The storage is freed at the end of the started task or
at initiator termination for subpool 236 and at the end of the job
for subpool 237. The NSHSPL and NSHSPV parameters on the ATTACH or
ATTACHX macro invocation used to create the currently active task
determine ownership of the subpool. If the currently active task was
given ownership of the subpool, then the TCB of the currently active
task owns the storage in this subpool. If the currently active task
is sharing this subpool with the attaching task, then the TCB of the
attaching task owns the storage in this subpool.
For more information, see the description of the ATTACH and ATTACHX macros in z/OS MVS Programming: Authorized Assembler Services Reference ALE-DYN and the virtual storage management topic in z/OS MVS Programming: Assembler Services Guide. For additional information about the SWA, see z/OS MVS Initialization and Tuning Guide.
- If a GETMAIN macro is issued in AMODE 31 for a DREF subpool, the LOC=BELOW parameter is ignored. VSM gives the user storage above 16M.
- Central storage backing this subpool can be pageable 1 MB page frames.
These subpools can coexist on the same
page of storage.
- These subpools can coexist on the same
page of storage.
- These subpools can coexist on the same
page of storage.
- These subpools can coexist on the same
page of storage.
- Storage is getmained in subpool 253.
- Storage is getmained in subpool 254.
- Storage is getmained in subpool 255.