z/OS V1R6.0 DFSMS Access Method Services for Catalogs

SETCACHE||||vafter SETCACHE SUBSYSTEM OFF is issued. However, if there is no writeactivity to a duplex pair, and all cylinders are in synchronization, the pair is notset to suspended duplex state.The Storage Control destages all modified data from cache and NVS to DASD.|||||||||||||||||||||||||||||||||||||||Setting Caching Off for a DeviceSETCACHE DEVICE OFF sets device caching off for the specified volume. Cachefast write and DASD fast write operations stop for that device. Modified data forthe volume is destaged to the DASD. The cache fast write and DASD fast writevolume status is retained so that when cache is set on again, these functionsresume.Setting Nonvolatile Storage Off for the SubsystemSETCACHE NVS OFF deactivates the NVS. This command also disconnects theNVS battery on a 3990 Model 6, or 9390, or on a 3990 Model 3 with either RPQ8B0174 or 8B0175 installed. DASD fast write is stopped and all modified DASDfast write data is destaged to the appropriate volumes. Cache fast write data is notdestaged. Dual copy changed cylinder logging is terminated for dual copyvolumes, but both copies of dual copy volumes continue to be updated.Either a hardware failure in a duplex pair while the NVS is deactivated, or a utilitypower outage, or a loss of cache, or the cache being set off at this time causes allduplex pairs to be set to suspended duplex state at the next write I/O to each pair.Setting DASD Fast Write Off for a VolumeSETCACHE DASDFASTWRITE OFF sets DASD fast write off for the designatedvolume. All DASD fast write data for the specified volume is destaged.Setting Cache Fast Write Off for the SubsystemSETCACHE CACHEFASTWRITE OFF sets cache fast write off for the logicalDASD subsystem. All cache fast write data is destaged to the DASD.Resetting a Duplex Pair to Two Simplex VolumesSETCACHE RESETTOSIMPLEX terminates a duplex pair and restores bothvolumes to simplex operations. The primary volume retains the DASD fast writestatus of the dual copy logical volume. The secondary volume assumes the devicestatus defaults, unless the pair was suspended, in which case the caching status isinactive. Normally, all updates in NVS and cache are destaged to both the primaryand the secondary volumes.The primary volume contains copies of all updates to the volume. Because of aDASD fast write pending condition (probably due to another job), modified tracksmight not have been destaged to the secondary volume. If the volumes must beidentical, either use a utility program to compare the two volumes, or change thesecondary volume serial number using ICKDSF, vary it online, and copy theprimary volume to the secondary volume.Destaging All Modified Data in Cache and NVS to DASDSETCACHE DESTAGE specifies that all modified data in cache and NVS isscheduled for destage to DASD. This command is usually issued for shutdown andis included in the operator command Halt End of Day (Halt EOD).Chapter 31. SETCACHE 335