Logical WORM Considerations

Logical WORM is supported in all models of the TS7700 Virtualization Engine and was first introduced with Release 1.6 of the TS7700. To request a logical WORM volume, an outboard data class policy must be defined (at the library) requesting logical WORM. This data class must then be assigned through the ACS routines, for a logical WORM request. A logical volume becomes WORM when it is first mounted and written from load point. A volume does not have the WORM attribute if user data is already written to the volume. Also, when a data set written to a WORM volume extends to another volume (EOV processing), the next volume in the chain will also be WORM. It is handled through the existing advanced (outboard) policy management support. As with the 3592 physical WORM tape support, any attempt by the host to modify a previously written user data record of a logical WORM volume is failed by the TS7700.

With the 3592 WORM tape support, a volume is designated as WORM through usage of special WORM media types (MEDIA6, MEDIA8, MEDIA10, and MEDIA12). A logical volume (MEDIA1 or MEDIA2) is designated as WORM, not by the usage of a special WORM media type, but when it is first mounted and written from load point (and associated with a data class policy that has WORM functionality enabled at the library). As a result, a common scratch pool is used for both rewritable (R/W) and WORM requests. When a logical volume (R/W or WORM) is returned to scratch, it can be reused on a scratch (category) mount as either rewritable (R/W) or as WORM. As with the 3592 WORM tape support, a logical WORM volume is assigned a worldwide unique identifier (WWID) and is associated with a write mount count (WMC). During the mount, the TS7700 assigns a WWID and WMC to the volume.

In order to be consistent with the physical WORM and the special release actions that might be in place by the tape management system for the logical volume’s VOLSER to be reused (when a logical WORM volume expires), it must be returned to scratch and the reuse of the volume (as either WORM or rewritable (R/W)) must then occur as a scratch (category) mount. Subsequently, if the volume is reused as logical WORM, the library creates a new WWID and WMC for this new instance of the volume. If, instead, the expired WORM volume’s VOLSER is to be reused (from load point) by specific mount (and not by scratch mount), the volume must first be moved to scratch and ejected “purged” from the library. Then, the volume can then be entered (as a new logical volume) into the library as private and used as either WORM or rewritable (R/W). Also, when a previously used R/W volume expires, to be reused as logical WORM, it must also go through the logical WORM steps before if the volume is to be mounted by specific VOLSER (and not by scratch mount). In summary, a logical volume can become WORM when it is mounted as a scratch volume (category mount) or mounted by specific VOLSER and the VOLSER referenced is considered a new logical volume. Refer to your tape management system for its usage of the WWID and the WMC and for its handling of expired logical WORM volumes.