VSAM record-level sharing allows multiple levels of CF caching
for DFSMS cache structures that are defined in the active storage
management subsystem (SMS) configuration.
VSAM RLS has multiple levels of CF caching. The value of the SMS
DATACLAS RLS CF Cache Value keyword determines the level of CF caching.
All active systems in a sysplex must have the greater than 4K CF
caching feature before the function is enabled.
To set up RLS CF caching, use the following values:
- ALL or UPDATESONLY or NONE or DIRONLY for
the SMS DATACLAS RLS CF Cache Value keyword
To allow greater than
4K caching of DFSMS VSAM data sets open for RLS processing, you need
to make the following changes:
- You can change the value of the SMS DATACLAS RLS CF Cache Value
keyword if you do not want caching of all VSAM RLS data:
- ALL
- Indicates that RLS is to cache VSAM index and data components
in the coupling facility. ALL is the default.
- NONE
- Indicates that RLS is to cache only the VSAM index data. The
data components are not to be placed in the cache structure.
- UPDATESONLY
- Indicates that RLS is to place only WRITE requests in the cache
structure.
- DIRONLY
- indicates that RLS will not cache data or index part 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 local storage but data
or index CIs are not stored in the cache structure itself.
- VSAM honors the RLS CF Cache Value keyword only when you specify
RLS_MaxCfFeatureLevel(A) and all systems in the sysplex can run the
greater than 4K caching code.
To determine the code level on each
system in the sysplex and whether the RLS CF Cache Value keyword is
honored, use the D SMS,SMSVSAM, D SMS,SMSVSAM,ALL, and D SMS,CFCACHE()
operator commands. When DFSMS cache structures connect to the system,
VSAM RLS issues an IGW500I message to indicate that greater than 4K
caching is active. The cache structures connect to the system through
the first instance of a data set opened on each system.
- You can specify the following values for the RLS_MaxCfFeatureLevel
keyword:
- A—This value allows greater than 4K caching if all active
VSAM RLS instances in the sysplex have the correct level of code.
- Z—This is the default value if you do not specify RLS_MaxCfFeatureLevel
in the active SMS configuration. Greater than 4K caching is not allowed.
- RLS_MaxCfFeatureLevel keyword in the SETSMS command
- RLS_MaxCfFeatureLevel keyword in the SET SMSxx command
- RLS_MaxCfCacheFeatureLevel in the D SMS,OPTIONS command