IBM System/370 Guide

reorganization, and all processing programs that access the BDAM data
set, is necessary if a relative track or actual address reference is
used and fewer (or more) 3330 tracks are allocated to the data set
than before.
Subject to the restrictions stated in Section 10:05 and those
indicated for BDAM data sets, existing executable processing programs
can be used without change to process data sets that have been
transferred to 3336 packs. Nothing need be done to job control for
these programs if the cataloged procedures supplied with the language
translators are used, as long as the 3330 facility is specified as
a SYSDA device at system generation. otherwise, job control statements
must be changed to request 3330 devices and, optionally. any data set
characteristic changes., such as block size.. RPS support, as described
previously, is provided automatically.
User-written programs that use the EXCP level to access disk data
sets that have been transferred to 3336 packs may have to be modified
to reflect the characteristics of the data set on the 3336: a different
number of records per track, a different number of tracks per cylinder,
etc. All 2311 and 2314 CCW lists will operate on 3330 facilities
except those that are device or channel time dependent and those that
use the file scan commands, which are not available on the 3330. User-
written 2311 or 2314 error routines will not execute correctly and
must be modified. RPS commands have to be added by the user if this
support is desired for programs that use EXCP. (Note that the XDAP
macro will include support of RPS commands.)
Data sets currently located on 2301 Drum Storage can be placed on
2305 modules by means of a data set utility program. Unit specification
in the job control statements of existing programs that will access
the 2305 module instead of the 2301 drum must be changed. Also, to
reflect the smaller capacity of a 2305 track, it may be necessary to
alter the block size used. The latter can also be done via job control
statement alterations (without program reassembly) unless block size
was specified in the program itself or record length is larger than
2305 track size.
60: 10 PLANNING OPTIMAL SYSTEM PERFORMANCE, USING BLOCK MULTIPLEXER
CHANNELS AND RPS DEVICES
Block multiplexing, rotational position sensing, and multiple
requesting provide the user with another tool that can improve total
system throughput. However, the effectiveness of this tool for a given
installation depends largely on proper planning for its use. This
section indicates how to use block multiplexer channels and RPS devices
effectively.
The guidelines outlined indicate how best to configure a system
with rotational position sensing devices, how to plan job scheduling,
and what to consider when determining disk data set characteristics.
Explanations follow the statement of each guideline.
All guidelines presented are not necessarily practical for all
users. Each item should be evaluated in terms of the processing
requirements and hardware configuration of an installation.
SYSTEM CONFIGURATION AND GENERATION
System configuration and generation guidelines are as follows:
1. Multiple 3330 facilities should be placed on a single block
multiplexer channel.
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IBM System/370 Specifications

General

Brand	IBM
Model	System/370
Category	Server
Language	English