IMS in the Parallel Sysplex Volume I: Reviewing the IMSplex Technology

98 IMS in the Parallel Sysplex, Volume I: Reviewing the IMSplex Technology

– CQS abnormal termination

– CQS restart completion

– Structure copies

– Structure recoveries

– Structure overflow

– Work available on a shared queue

5.3.1 Base Primitive Environment

The Base Primitive Environment (BPE) is a software layer on which new components of IMS

are designed to be built on. It is the first step in the rearchitecting of IMS. BPE provides

common services, such as subdispatching, storage management, tracing, serialization, and

message formatting. BPE services are accessed through well-defined architected interfaces.

CQS is one of the first components built on the BPE software layer.

For the most part, BPE is not visible. IMS components are built on top of BPE, but BPE itself

has very few externals. The externals are:

򐂰 BPE modules in RESLIB

򐂰 Messages issued to the system console

򐂰 CQS JCL

򐂰 PROCLIB members

򐂰 BPE dump formatter

For information about setting up the BPE PROCLIB members, see

IMS in the Parallel

Sysplex, Volume III: IMSplex Implementation and Operations,

SG24-6929.

5.3.2 Components of a list structure

All the structures used in the Parallel Sysplex must be defined in the Coupling Facility

Resource Management (CFRM) policy, before they can be allocated. When the structures

related to shared queues are allocated by CQS, they will be allocated as list structures. The

type of the structure (cache, lock, list) is determined by the connector, not by the policy.

There are two pairs of structures in a shared queues environment — one pair for full function

messages and another pair for Fast Path EMH messages. Each pair consists of a primary

structure and an optional overflow structure. The overflow structure is used to offload

messages from the primary structure when it is in danger of becoming too full.

The EMH structure pair is needed only if IMS system generation includes the FPCTRL macro,

enabling Fast Path. If the IMS system definition includes the FPCTRL macro, the EMHQ

structure is always required. There are cases where the IMS system definition has the

FPCTRL macro and EMH is not being used to process transactions, such as with Fast Path

DEDB databases being used. The EMHQ structure is still required because Fast Path

transactions could be implemented through an online change if the system has been defined

as Fast Path capable. If the system is defined as Fast Path capable, and you do not process

EMH transactions, your EMHQ structure can be defined as the minimum size of 256K.

Shared queues structures are persistent. They remain allocated even if all CQSs have

disconnected, or all IMSs and their associated CQSs cold start.

Note: When migrating CF levels, lock, list, and cache structure sizes might need to be

increased to support new function. For example, when you upgrade from CFCC level 9 to

level 10, the required size of the structure might increase by up to 768 K. Flexibility is a

good convention to specify for both the initial and maximum sizes in CFRM.