From Page 4 of the Data Class Define panel, use the DOWN command
to view Page 5, on which you specify Shareoptions and RLS attributes.
- Shareoptions
- Specifies how end
users can share a component or cluster.
The Xregion value specifies
the amount of sharing allowed among regions within the same system,
or within multiple systems using global resource serialization (GRS).
You can specify the following values:
- 1
- Any number of users can read the data set at one time, or only
one can write to it. This setting does not allow any type of non-RLS
access when the data set is already open for RLS processing.
- 2
- Any number of users can read the data set at one time, and only
one can write to it. If the data set is already open for RLS, non-RLS
users can read the data set but cannot write to it. If the data set
has been opened for non-RLS output, an RLS open fails.
Requirement: You must apply
APARs OW25251 and OW25252 to allow non-RLS read access to data sets
already open for RLS processing.
- 3
- Any number of users can share the data set, and each is responsible
for maintaining read and write integrity. This setting does not allow
any type of non-RLS access when the data set is already open for RLS
processing.
- 4
- Any number of users can share the data set, and buffers used for
direct processing are refreshed for each request. This setting does
not allow any type of non-RLS access when the data set is already
open for RLS processing.
The Xsystem value specifies the amount of sharing
allowed among systems. You can specify the following values:
- 3
- Any number of users can share the data set, and each is responsible
for maintaining read and write integrity.
- 4
- Any number of users can share the data set, and buffers used for
direct processing are refreshed for each request.
If values are not specified explicitly or in the data
class, VSAM defaults are used.
- RLS CF Cache Value
- Specifies
the amount of data that will be cached. This keyword is honored only
when RLS_MaxCfFeatureLevel(A) is active in the sysplex.
DFSMS CF
cache structures are connected to the system when the first VSAM RLS
instance is opened on the system. At this time, message IGW500I is
issued to indicate whether the RLS CF Cache Value keyword is honored.
You
can specify the following values:
- ALL
- Indicates that VSAM index and data components will be cached. ALL is
the default.
- NONE
- Indicates that only the VSAM index data will be cached. The data
components will not be placed in the cache structure.
- UPDATESONLY
- indicates that only WRITE requests will be placed in the cache
structure.
- DIRONLY
- indicates that RLS will not cache the data or index parts of
the VSAM data set in the coupling facility cache structure. In this
case, RLS will use the XCF cache structure to keep track of data that
resides in permanent storage (DASD) and in local storage but
data or index CIs are not stored in the cache structure itself.
- RLS Above the 2-GB Bar
- Specifies
whether the SMSVSAM address space can take advantage of 64-bit addressable
virtual storage during VSAM RLS buffering.
You can specify the
following values:
- Y
- Indicates that VSAM RLS buffers can reside above the 2-gigabyte
bar. This setting is recommended for best performance of high-volume
applications that use VSAM RLS buffering.
- N
- Indicates that VSAM RLS buffering is limited to storage below
the bar. N is the default.
- Extent Constraint Removal
- Specifies
whether data sets are allowed to be extended beyond 255 extents.
- CA Reclaim
- Specifies whether the
DASD space for empty control areas (CAs) will be reclaimed for key-sequenced
data sets (KSDS). Specify one of the following:
- Y
- Indicates that DASD space for empty CAs will be reclaimed. This
is the default.
- N
- Indicates that DASD space for empty CAs will not be reclaimed.
The value for CA Reclaim is always saved in the
catalog, but is used only if the CA reclaim function is enabled in
the IGDSMSxx member of PARMLIB or with the SETSMS command.
The
setting for CA Reclaim for a data class is processed only when a catalog
entry for a KSDS is defined. If you need to change the CA reclaim
setting for an existing KSDS based on the contents of the data class,
either use the ALTER command for the KSDS or delete and define the
KSDS to use the value in the data class.
For
more information, see the topic about CA reclaim in z/OS DFSMS Using Data Sets.