S/390 PartnerWorld for Developers, ITSO/EFS Project EFS Systems on a Linux Base: Additional Topics

Chapter 8. z/OS base sysplex on z/VM 101

Global Resource Serialization (GRS) is used to extend ENQ processing to SYSTEMS

(all-members) scope and optionally to convert reserve/release requests that normally

serialize access to an entire volume to ENQ/DEQ requests that serialize specific data set(s).

GRS also uses CTCs to communicate among the members.

8.2.3 What a Parallel Sysplex® is

A Parallel Sysplex looks a lot like a base sysplex, but uses an IBM Coupling Facility (CF) for

signaling among systems. A parallel sysplex extends base sysplex functionality by storing

and retrieving lists of data contained in coupling facility structures. CF structures are used to

implement extended catalog facilities, workload balancing, subsystem functions (for

subsystems like JES2, DB2, CICS, and IMS), and a common system log, among others. CF

can be run only on selected IBM System/390 and z/Series processors.

8.2.4 Why run a base sysplex

Using a Base Sysplex on an EFS system offers advantages in the following areas:

򐂰 Ease of maintenance

򐂰 Isolation

򐂰 Throughput

򐂰 Single-control point

򐂰 Approximation of customer environments

Base sysplex offers the advantages of running more than one z/OS system without requiring

the overhead and work of maintaining separate z/OS installations. Each member of the base

sysplex may be initialized using the same residence volumes and master catalog. Only one

set of target and distribution library data sets needs to be maintained.

The base sysplex offers the ability to isolate workloads from each other; for example, some

programmers might use one image to develop and bench-test code while others use a

second image for integration testing, and a third image runs other work. If one image fails or

is damaged by testing, the other(s) may continue to run.

Global Resource Serialization (GRS) provides systems-scope ENQ/DEQ for members of the

sysplex. GRS may be implemented without defining a base sysplex, but a sysplex cannot be

defined without activating GRS. Under GRS, only the target data set is serialized--remaining

data on a volume may be accessible to other jobs and users. Improvements in throughput are

relative to a shared-spool, shared-DASD configuration that uses reserve/release to protect

shared data. When large numbers of System/390 processors are available (four or more), our

experience suggests that base sysplex may improve overall throughput.

The base sysplex allows an operator to monitor and control all systems from one console.

Commands may be routed to specific systems or broadcast to all systems.

Many EFS systems are used by independent software vendors (ISVs); testing using a base

sysplex may more closely approximate their customers’ environments.

8.3 FLEX-ES system definitions

Our FLEX-ES system definition for running z/VM was:

system sys1:

feature lpar

lparnum(1)

memsize(0x1F0000)