Does the new parameter ENQDSN CAIACFxx Parmlib Member alter the way GRS is currently handling the ENQ's?'
Article ID: 44578
Updated On:
Products
Issue/Introduction
Does the new parameter ENQDSN CAIACFxx Parmlib Member alter the way GRS is currently handling the ENQ's?'
Environment
Component: ACF2MS
Resolution
The answer depends on a site's current GRS exclude list.
Specifying the ENQDSN parameter overrides the internal ENQDDN processing.
Using ENQDSN can help reduce contention for users who run multiple CA ACF2
databases in the same sysplex and choose to to 'convert the ACFVSAM RESERVE'.
A sample CA ACF2 exclude list for GRS is constructed as follows:
* LABEL TYPE, MINOR?LENGTH, MAJOR?NAME, MINOR?NAME
RNLDEF RNL(EXCL) TYPE(SPECIFIC) QNAME(SYSDSN) RNAME(ACF2.LOGONIDS)
RNLDEF RNL(EXCL) TYPE(SPECIFIC) QNAME(SYSDSN) RNAME(ACF2.ALTLIDS)
RNLDEF RNL(EXCL) TYPE(SPECIFIC) QNAME(SYSDSN) RNAME(ACF2.RULES)
RNLDEF RNL(EXCL) TYPE(SPECIFIC) QNAME(SYSDSN) RNAME(ACF2.ALTRULES)
RNLDEF RNL(EXCL) TYPE(SPECIFIC) QNAME(SYSDSN) RNAME(ACF2.INFOSTG)
RNLDEF RNL(EXCL) TYPE(SPECIFIC) QNAME(SYSDSN) RNAME(ACF2.ALTINFO)
RNLDEF RNL(EXCL) TYPE(GENERIC) QNAME(ACFVSAM)
RNLDEF RNL(EXCL) TYPE(GENERIC) QNAME(SYSVSAM) RNAME(ACF2)
RNLDEF RNL(EXCL) TYPE(GENERIC) QNAME(SYSDSN) RNAME(ACF2)
Note: The last GRS exclude entry can be used if the RNAME is only used with the database clusters.
The general recommendation is to exclude(Not convert as shown above) ACFVSAM
however sites wanting to 'convert the ACFVSAM reserve' can remove the following
line from the GRS exclude list recommendations:
RNLDEF RNL(EXCL) TYPE(GENERIC) QNAME(ACFVSAM)
The following applies to sites that do not exclude ACFVSAM and choose to
'convert the ACFVSAM RESERVE'.
To simplify the following explanation the following will focus on the
ACF2 LOGONIDS database but the same holds true for the other two ACF2
databases.
Prior to the introduction of the ENQDSN option all the ACFVSAM SYSTEMS ENQ
requests contained a hardcoded minor name of LOGONIDS. This meant that
when the ACFVSAM ENQ was no longer excluded from GRS processing, an
EXCLUSIVE ACFVSAM ENQ would lock out all systems in the GRS ring/star
configuration even though other systems could be accessing different
ACF2 LOGONIDS databases due to the hardcoded minor name.
With the introduction of ENQDSN, the minor name on the ACFVSAM SYSTEMS
ENQ represents the 44 character database name. The assumption is that
each set of ACF2 databases will have unique names within the GRS
configuration. For example you have 2 ACF2 LOGONIDS in a GRS configuration
of SYS1.ACF2.LOGONIDS.SYSTEMA and SYS1.ACF2.LOGONIDS.SYSTEMB. An EXCLUSIVE
ACFVSAM ENQ issued by a system against SYS1.ACF2.LOGONIDS.SYSTEMA
will only cause the systems sharing that specific database to wait for
the ENQ to be released. The other systems accessing
SYS1.ACF2.LOGONIDS.SYSTEMB will not be affected by the EXCLUSIVE ENQ.
The same contention described above for systems running without ENQDSN
will occur for identically named datasets in a GRS configuration in which
the databases are actually different. This is because the minor name on
the ACFVSAM ENQ is only differentiated by the dataset name with the
ENQDSN option. Those systems accessing the duplicate named dataset(s)
will wait for the ACFVSAM EXCLUSIVE ENQ to be released even though they
maybe accessing a direct ACF2 database with the same name.
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