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Maintaining the DSN Catalog (TSIDUTL) Introduction

Chapter. 6 Additional BIM-EPIC Utilities 6-3

BACKUP identifies the DSN Catalog backup for BACKUP and RESTORE.

FASTDS identifies the DSN Catalog backup for FASTBU and FASTRS.

IJSYSDS identifies the DSN Catalog dataset, sometimes required for FASTBU and FASTRS.

WORK identifies a temporary dataset required by the scratch and restore functions

(SCRATCH, TSCRATCH, DSCRATCH, PSCRATCH, and RESTORE). Its size is

dependent on the number of tape volumes containing OFFLOAD, MCAT, or sub-dataset

versions. Allow 50 bytes per volume.

When using the VSE/VSAM Space Management for SAM feature to manage the WORK file

required by the RESTORE and SCRATCH functions, an additional consideration is necessary

to avoid failures ranging from minor annoyances to partial catalog corruption. See the

WORK File and VSE/VSAM Space Management For SAM discussion immediately following.

When using the VSE/VSAM Space Management for SAM Feature to manage the SAM file

(filename WORK) required by the EPIC utility TSIDUTL program for both the RESTORE

and SCRATCH functions, an additional consideration is necessary.

This WORK file is used as both output and input to accomplish the requested task and expects

only the data written from the current execution to be read back. In the case of the RESTORE

function, this file is used as a temporary storage area for data pertaining to each sub-dataset

restored to the DSN Catalog. In the case of the SCRATCH function, this file is used as a

temporary storage area for data pertaining to the scratching of all multi-dataset tape volume

serial numbers.

When this WORK file is specifically allocated to VTOC controlled space using typical DLBL

control statements reflecting the SD type of file label code (which is also the default if not

specified) and opened for output, standard VSE routines (LIOCS) assure that any previously

existing data found in the disk space is physically erased before the new data is actually

transferred to the disk device.

The VSE/VSAM Space Management for SAM Feature does not perform in exactly the same

manner but rather uses the DISP operand as a basis for many of its decisions. This DISP

operand can contain up to three positional keywords to tell VSAM how the dataset is to be

opened and disposed of given either normal or abnormal termination. The key difference here

is that VSAM ignores the fact that a dataset is being opened for output when the dataset

already exists and uses the first DISP keyword to determine if the existing should be erased

before new data is entered into the dataset (DISP=NEW) or append new data following the

existing data (DISP=OLD). Note that if the dataset is being opened for output and the dataset

does not already exist, use of either DISP=NEW or DISP=OLD will give identical results

since there is no existing data to be appended.

The problem arises only when a program uses the same DTF name (in this case WORK) for

both output and input in a single execution. Under this condition, only the DISP=OLD

operand can be specified which says do not erase any existing data but rather append new data

behind any old data that may already exist. If DISP=NEW was specified, the initial open for

output would automatically erase any existing data but failure would result when the attempt

to open the file for input was attempted (DISP=NEW and open for input are incompatible and

WARNING!

WORK File and

VSE/VSAM Space

Management for

SAM Feature

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