IBM Support

Use of VSAM shareoption ( SHR ) with IWS for z/OS

Troubleshooting


Problem

Cases for use for shareoption (2) or shareoption (3) with IWSz VSAM files

Cause

Revised and simplified October 12, 2017

Resolving The Problem

Some suggestion related the use of shareoption

1) VSAM suggests to use shareoption(2) to prevent VSAM integrity errors: in that case it is directly VSAM that ensures write integrity

2) IWSz uses shareoption(3) in the shipped samples (EQQPCS01) for its VSAM datasets : it is IWSz that ensures write integrity in the case standard IWSz features and proper IWSz customizations are used and no methods external to IWSz (such as a VSAM editor) are used to update the VSAM files while the IWSz
controller is active. BATCHOPT parameter CHECKSUBSYS must be set to CHECKSUBSYS(YES) if
the controller is running as mentioned in the Customization and Tuning Guide.

3) If IWSz is instead running in a situation where shareoption(2) must be used, or if it is decided by the Customer to use shareoption(2), it needs to be considered that the consequent VSAM overhead might be the origin of performance degradation.

4) In case the performance degradation is not a problem (we cannot act on them, it is VSAM processing), SHR(2) is a more prudent setting which can be used in place of SHR(3) except for the following files
which MUST always use shareoption(3): EQQADDS ( AD ), EQQOIDS ( OI ), EQQSCPDS ( SCP ) .

This means the following files can be set to shareoption(2) :
EQQCP1DS, EQQCP2DS, EQQCXDS, EQQNCPDS, EQQNCXDS, EQQJS1DS, EQQJS2DS,
EQQRDDS, EQQSIDS, EQQLTDS, EQQLTBKP, EQQLDDS, EQQNXDDS, EQQXD1DS,
EQQXD2DS, EQQNSTDS, EQQSTDS,EQQWSDS

(5) For special considerations regarding the AD and OI databases see technote
http://www-01.ibm.com/support/docview.wss?uid=swg22009558
(Special considerations for the prevention of VSAM corruption of the AD database ( EQQADDS ) and OI database ( EQQOIDS ))

(6) For identification and recovery actions in case corruption is suspected see technote
http://www-01.ibm.com/support/docview.wss?uid=swg22009568
(Identifying possible corruption of IWS z/OS VSAM files)

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Document Information

Modified date:
13 September 2019

UID

swg21198958