IMS Version 8 Implementation Guide A Technical Overview of the New Features

54 IMS Version 8 Implementation Guide

Assuming that database CUSTDB1 has 3 DBDS defined for (as pictured in Example 4-3),

consider the following GENJCL input:

GENJCL.IC DBD(CUSTDB1) COPIES(2) SMSNOCIC(4,S,C) ONEJOB DBREL(L)

This invokes the Image Copy 2 tool with the control statements in one execution step as

shown in Example 4-4.

Example 4-4 IC2 control cards

|...+....1....+....2....+....3....+....4....+....5....+....6...

//SYSIN DD *

2 CUSTDB1 DDNAME1A ICOUT11 ICOUT12 XLC4

S CUSTDB1 DDNAME1B

S CUSTDB1 DDNAME1C

The necessary skeletal JCL changes introduce the new keywords:

%SMSGRPA numeric value which controls group processing

%SMS1DSA numeric value indicating whether SAMEDS was specified

%GROUPA character value containing the group name or null

If you leave column one and column 61 blank, you are invoking the Image Copy 2 utility

without any use of the new features. However, you can use the existing skeletal JCL as

provided for exploiting as well as omitting the enhancements.

4.2 Parallel database processing

The parallel database processing enhancement is provided for improving the performance of

IMS after restart to reach a steady state faster. Multiple TCBs (using multiple threads) are

used for database authorization, dynamic allocation, open, close and end-of-volume

processes, which were running as serialized processes before. The parallel database

processing provides the following benefits:

򐂰 Exploits available processor power

򐂰 Reduces the elapsed processing times

򐂰 Achieves faster steady state response times

The parallel database processing is implemented by automatically exploiting additional

multiple task control blocks (TCBs). The parallel database processing is supported for full

function databases only. 10 TCBs are used in parallel. IMS uses an algorithm to divide the

DBREL( L | P ) if SMSNOCIC is

specified

‘L’ or ‘P’ in column 59 for logical or physical processing

(*) smsopts in any order, following

the SMSCIC(smsopts) or

SMSNOCIC(smsopts) parameter

SAMEDS, COMPRESS, OPTIMIZE

SAMEDS ‘S’ in column 1, multiple Image Copies into same single

output data set

COMPRESS ‘C’ in column 60 for compression mode

n [1,2,3,4] ‘n’ in column 61, applies the value for the OPTimize(n) option

Note: IMS Database Image Copy 2 enhancements require concurrent-copy capable DASD

controllers.