Memorex LOCK - VERSION 2-24 Informacje Techniczne Pobierz pdf (Strona 52)

Managing Disk Devices

1-34 User Reference

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Managing Disk Devices

Disk Pooling BIM-EPIC uses disk pooling to make disk allocation more flexible and

more efficient. The systems programmer defines disk pools to use in your

installation. Disk pools can include one or more disk volumes. In

addition, part of a volume can be allocated to a disk pool.

Each disk dataset must be assigned to a disk pool before allocation. Each

time a dataset version is written, an allocation is made in that pool. Disk

pools are referenced using a six-character pool name. However, the same

pool can also be referenced by alias pool names. In addition, you can have

CPU and partition-independent pool names. If these pools are defined,

you can reference a partition independent pool by adding two dashes to

the end of the name, for example, P O O L - -. For CPU and partition

independent pools, add three dashes to the end of the name, for example,

P O O L - - -.

Pool names are assigned to datasets using JCL or the DSN Catalog.

Leveling Leveling reduces head contention by distributing allocations over the

entire disk pool, rather than concentrating the allocations on a single

volume. Each time a new extent is written, BIM-EPIC makes the

allocation on the next volume in the pool sequence. To minimize disk

fragmentation, leveling uses a “best fit” algorithm to allocate space. For

example, you need to allocate 3,000 tracks. Pool disk 1 has 12,000

contiguous tracks, disk 2 has 5,000 contiguous tracks, and disk 3 has 4,

000 contiguous tracks. The allocation will be made on disk 3 since that is

the “best fit.” If disk 1 is the only disk that has at least 3,000 contiguous

tracks, the allocation will be made on disk 1. Leveling is activated for a

disk pool when the pool is defined.

Offload Utilities The BIM-EPIC offload utility moves datasets from disk to tape and back

again. Processing is done logically, so you can use the offload utility for

backup, to reorganize your disk space, or just to offload infrequently used

datasets. BIM-EPIC automatically reloads to a temporary disk dataset

whenever needed. For offload actions, the only restriction is that the

offload utility processes be controlled sequential datasets. For backup

actions, the offload utility also processes Start Track 1 sequential datasets.

VTOC Utilities BIM-EPIC provides three utilities for displaying and updating VTOC

entries:

 TSIDLVT lists VTOC entries in batch mode.

 TVTO, a CICS transaction, displays the entries online.

 TSIDVUT allows you to modify existing VTOC entries.

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Memorex LOCK - VERSION 2-24 Informacje Techniczne Strona 52