Storage, Scratch, and Queue Management › Using Storage Pools

Using Storage Pools

To facilitate online programming and intertask communication, CA IDMS provides storage management functions that allow you to acquire space explicitly in storage pools.

These functions control allocation of variable storage in a CA IDMS storage pool or work area. Shared by system and user programs, the storage pool also contains space for buffers and initial storage areas (ISAs) used by Assembler and PL/I programs.

Note: All variable-storage entries (except COBOL LINKAGE SECTION and PL/I BASED storage entries) defined by your program are acquired automatically from the CA IDMS storage pool when the program starts and released automatically when the program ends.

Using CA IDMS storage management functions, you can:

• Acquire variable storage from a storage pool
• Establish addressability to previously acquired variable storage
• Release all or part of previously acquired variable storage

Types of Acquired Storage

You must specify whether the acquired storage is available to other users:

• User storage is available only to the issuing task; no other tasks can access it. CA IDMS maintains user storage through the issuing task's task control element (TCE).
• Shared storage is available to all tasks running under the CA IDMS system. CA IDMS links shared storage to the common system area (CSA) as well as to the TCE, as illustrated in the figure below. CA IDMS uses the CSA to locate the address of a shared area to satisfy requests from other tasks for shared storage.

  Note: Shared storage is available to all tasks within the CA IDMS system; however, each task must explicitly establish addressability to access such storage.

TCE and CSA Ownership

Shared storage is linked to both the TCE and CSA; user storage is linked only to the TCE, as the figure below shows.

┌─────────┐                  ┌───────────┐
│         │ STORAGEID='WRK1' │           │
│  TCE    │ Shared           │    CSA    │
│ (Task1) │                  │           │
│         │                  └─┬─────────┘
│         ├────────────────┐   │                    Storage pool
└─────────┘                │   │    ┌───────────────────────────────────────────┐
                           │   │    │                                           │
                           │   │    │                                           │
                           │   │    │                                           │
┌────────┐                 │   └────►─────────┐                                 │
│        │ STORAGEID='WRK2'└────────►  WRK1   │                                 │
│  TCE   │ User                     ├─────────┴──────────┐                      │
│ (Task2)├──────────────────────────►  WRK2              │                      │
│        │                          ├────────────────────┘                      │
│        │                          │                                           │
└─────────┘                         └───────────────────────────────────────────┘

Kept Storage

If you require that storage remain allocated after a task ends, it should be assigned the KEEP attribute when it is initially allocated. Kept storage is associated with the logical terminal on which the task is executing and with the task itself; such storage can be released only through a program request.

Releasing Storage

When storage is explicitly released or a task terminates, CA IDMS releases linkage to the TCE.

For a quick reference of storage release procedures and conditions, see Storage Pool Summary.

'User storage only'. You can explicitly release all or a part of user storage. For a partial release, TCE linkage and the KEEP attribute remain unaffected.