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What is the disadvantage in using TYPE=SHR for TSO sessions in TPX.

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Article ID: 215153

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Updated On:

Products

TPX - Session Management

Issue/Introduction

In TPX application characteristic table (ACT) the virtual terminal TYPE's that can be defined for application sessions is SHR, GRP or UNQ.
A TYPE=TPX is ONLY used for TPX prefixed applications, such as TPXADMIN, TPXOPER ...etc.
What's the recommended TYPE for TSO applications.

Environment

Release : 5.4

Component : CA TPX for Z/Os

Resolution

TYPE SHR can only be used with applications that support concurrent parallel sessions with same session partners known as parallel sessions.

Multiple concurrent sessions between the same two LUs are referred to as parallel sessions. Not all LUs have parallel session capability.

Most applications do not support parallel sessions. 
TSO can support parallel session. However, that means no TSO reconnect will be possible.

"TSO's RECONNECT processing requires more than one CLSDST PASS. 
To accommodate this requirement, the virtual terminal pool definition must include 
the DEDICATE parameter, which does not allow parallel sessions or ACB-sharing."

Shared (SHR) ACB for TSO is not advisable, since reconnect function would not be possible.
To use TPX SHARED ACB and TSO, TSO must be configured to allow parallel session, which means no TSO reconnect. 

For TSO, use GRP (Group) virtual terminals (recommended).