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Record-level sharing CF caching z/OS DFSMStvs Administration Guide GC52-1388-00 |
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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. Before z/OS Version 1 Release 3, VSAM RLS placed the data of a VSAM sphere in the CF cache structure only when the sphere's CI size was less than 4K. For CIs greater than 4K, VSAM RLS placed the first 2K in the CF cache (to utilize the cross-invalidate features of the coupling facility). To retrieve a CI that was greater than 4K, VSAM RLS processing would always read the data from a direct access storage device (DASD) volume. Since z/OS Version 1 Release 3, 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. The default value, ALL, indicates that RLS caches all data for a sphere in the coupling facility (for both index and data parts of the sphere). If you specify NONE, then RLS caches only the index part of the VSAM sphere. If you specify UPDATESONLY, then RLS caches data in the coupling facility only during write operations. All active systems in a sysplex must have the greater than 4K CF caching code installed before the function is enabled. To set up RLS CF caching, use the following values:
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