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

Chapter 14. Sysplex terminal management 195

– All static terminals with SRM=LOCAL:

When SRM=LOCAL, end-user significant status is known only to the local IMS.

– Dynamic STSN terminals with SRM=LOCAL:

Unlike ETO non-STSN terminals, for ETO STSN terminals, the SRM is set at logon

time, so IMS knows whether SRM is LOCAL or not. If it is LOCAL, then IMS will want to

manage the VGR affinity since it will be the only IMS to know whether the user has

end-user significant status.

Table 14-1 summarizes how IMS sets VGR affinity management.

Table 14-1 VGR affinity management

The existence of command significant status, when a resource structure exists, does not

affect the deletion of a VGR affinity. Because command significant status is always GLOBAL

when a structure exists, command significant status can always be recovered on another IMS

in the IMSplex. When no resource structure exists, then command significant status is always

LOCAL and will prevent the deletion of a VGR affinity.

14.7 Resources and the resource structure

The resource structure is used keep information about the IMSplex and its members (IMS,

CQS, and the RM), about global IMSplex processes (such as the global online change

process), and about individual terminal and user resources. This section describes those

resource entries used for the sysplex terminal management function, including when they are

created, what data they contain, how they are used, and when they are deleted.

14.7.1 Resource structure components and characteristics

When a connector connects to a structure defined in the CFRM policy, that connector

identifies the type of structure (list, cache, or lock) and its characteristics. For the resource

structure (and for the shared queues structures), the Common Queue Server (CQS) is the

connector. Some of the characteristics of the resource structure specified by CQS are:

򐂰 How many List Headers (LH)

The resource structure is allocated with 192 list headers. A list header is an anchor point

for list entries.

򐂰 What type of List Entry (LE)

Each list entry represents one IMSplex or terminal/user resource on the structure. Each

list entry is composed of several parts.

Terminal Type SRM Managed by

Static Global, None VTAM

Dynamic STSN Global, None VTAM

Dynamic non-STSN Any VTAM

Static Local IMS

Dynamic STSN Local IMS

196 IMS Version 8 Implementation Guide

– List Entry Controls (LEC)

Header for each list entry. The LEC contains information about list entry, such as:

• Entry Key (ENTRYKEY):

For RM, the entry key is the “resource type” plus “resource name” (for example,

x’01’ + trancode). When RM asks CQS to create an entry, CQS uses the resource

type to identify a range of 11 list headers, and the resource name to determine

which LH in that range on which to place the list entry. The entry key does not have

to be unique, although for the resource structure, RM keeps them unique.

• User-managed List Entry ID (LEID):

The LEID is the “name type” plus “resource name” (for example, x’01’ plus LTERM

name). The LEID must be unique within the structure. STM uses this characteristic

to enforce resource type consistency.

• Version:

Number incremented by one each time the resource entry is updated. This is used

by RM to ensure that updates to the structure are serialized.

• Other:

There are several other fields in the list entry controls that are used by CQS, XES or

the CFCC to manage the structure. They are not of interest for this discussion.

– Adjunct area (ADJ):

This is optional for list structures in general, but for the resource structure, every list

entry has one. The adjunct area is 64 bytes and contains the resource “owner” and a

small amount (up to 24 bytes) of client data (DATA1).

– Data elements (DE):

Data elements are also optional for a list structure, but when defined, are used to

contain user data that is too large to fit in the adjunct area. The resource structure is

defined with 512 byte data elements. Each list entry may have zero or more data

elements, containing recoverable resource data (DATA2) that is too large to fit in

DATA1.

򐂰 Other characteristics of the resource structure include:

– Structure is persistent:

Will not be deleted when all connectors are gone.

– Connection is persistent:

Will not be deleted if connector abends.

– Supports (new) structure management enhancements. See Chapter 10, “Coupling

Facility structure management” on page 137 for a description of the following

enhancements.

• Alter and autoalter

• System managed rebuild

• System managed duplexing