What follows is a list of RLS enhancements. The majority of them are introduced in z/OS DFSMS 1.3.
RLS/KSDS extended addressability
When VSAM RLS support was announced with DFSMS/MVS V1R3, it did not support VSAM KSDS extended addressability (EA) format. In other words VSAM RLS component retained the 4 GB architectural limit for the component size imposed by using the 4-byte field for the relative byte address (RBA) addressing mechanism. DFSMS/MVS V1R4 removed this restriction by supporting RLS EA for VSAM KSDSs, and therefore VSAM RLS now supports VSAM KSDSs up to the current multivolume limit of 59 DASD volumes.
As in VSAM non-RLS extended addressability, a VSAM RLS extended addressability KSDS must have its data class defined with:
Data Set Name Type =EXT
If Ext =P or R
Extended Addressability =Y
VSAM RLS CF structure duplexing and rebuild
VSAM RLS goes to lost locks state when the CF lock structure is lost and a system is also lost — a disruptive condition.
This process consists of the lock structure rebuild with all of the active VSAM RLS instances with the steps of allocating a new structure instance, propagating the lock data to the new structure, and switching over to using the new structure instance.
Currently, z/OS supports four types of lock structure rebuild processes. They are
This enhancement to the current user-managed rebuild process will minimize the possibility of running out of record table space. Prior to this enhancement, if record space is exhausted, either an 0F4 abend or a record management error will occur. This enhancement adds a new validation check function during the user-managed rebuild process for the lock structure. When rebuild tries to change a lock structure and the size of the record table is greater than 50%, this new function will determine if the new table has enough space for all existing record table entries, plus enough empty space for future locking processes (120%). If the answer is no, then the rebuild request is rejected and a new IGW457I message will be displayed.
System-managed duplexing rebuild
This support is available from z/OS V1R4 DFSMS. The VSAM RLS duplexing support only applies to the lock structure and not the cache structures.
What is it?
This facility is a hardware-assisted mechanism for VSAM RLS duplexing CF lock structure data, and provides a robust recovery mechanism for failure scenarios such as a loss of a CF, or loss of connectivity to a single CF.
How to set it up?
To use the new VSAM RLS system-managed duplexing function the following tasks are required:
Review CF configuration
Evaluate the CF configuration (storage, links, processor capacity) and make any necessary configuration changes to accommodate the new VSAM RLS lock structure instances resulting from system-managed duplexing.
Migrate to z/OS V1 R4 or later
All systems in the sysplex that use this function will need to be upgraded to this level that supports System-managed duplexing.
Install hardware CFCC level 12 or later
CF Duplexing requires CFCC Level 12 for implementation on IBM ~ zSeries servers. For G5/G6 Servers and the stand alone CF 9672-R06, CF Duplexing function requires CFCC Level 11.
Format the CFRM couple data set
Format this as system-managed, duplexing-capable, and bring that CFRM couple data set into use in the sysplex, to enable CFRM for system-managed duplexing.
Modify the CFRM policy
Modify this to control the sizing, placement (through the CF preference list) and the DUPLEX parameter indication for the VSAM RLS lock structure, which is duplexed via system-managed duplexing, and activating this CFRM policy.
RLS CF caching enhancements
This support is available in z/OS V1 R3.
What is it?
There are two RLS caching enhancements, respectively:
How to set it up?
Here are the steps to take.
Migrate to z/OS V1 R3 or later
You must be at this level or higher.
Update SYS1.PARMLIB member IGDSMSxx
There are two new keywords in IGDSMSxx. They are:
RLS_MAXCFFEATURELEVEL is a sysplex wide value. The first system activated in the sysplex will set the value; all other systems will use the value set by the first system. Default: Z.
– RLS_MaxCfFeatureLevel(A) indicates that VSAM RLS caching uses the characteristics specified in the SMS DATACLASS defined for the VSAM sphere.
– RLS_MaxCfFeatueLevel(B) indicates that DynamicCfCacheReassignment is installed. This feature is active if the RLS_DynamicCfCacheReassign(YES) is specified in the active SMS parmlib member.
– RLS_MaxCfFeatureLevel(AB) indicates that both features may be activated.
Update data class
The new caching characteristics are defined in the DATACLASS SMS construct. A new field is added to the ISMF DATACLASS construct called RLSCFCACHE.
The values are NONE, UPDATESONLY, and ALL(default).
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