The write-once, read-many (WORM) function of tape data storage is accomplished on the 3592 models through a combination of microcode controls in the drive and special WORM tape cartridges. The 3592 WORM media types are MEDIA6, MEDIA8, MEDIA10, and MEDIA12.
When the drive senses that a cartridge is a WORM cartridge, the microcode prohibits alteration of user data already written on the tape by means of an overwrite-protection pointer stored in the cartridge memory (CM). Statistical Analysis and Reporting System (SARS) data can be written and updated on WORM tapes because the SARS data is not in the user area of the tape. Each WORM cartridge is identified using a world-wide unique cartridge identifier (WWCID), which is permanent and locked, providing another level of security for data that must be maintained. This permanent locked information is stored in both the cartridge CM and on the tape itself, and can also be associated with the unique barcode VOLSER.
While the overwriting of data is not allowed on a WORM cartridge, appending of data is allowed under certain conditions. For example, an additional file can be appended following the last file on a tape. Records can also be appended to the last file written on the tape.
In the system-managed tape library environment (ATLDS or MTL), WORM media is not mounted by default to satisfy a scratch mount request. WORM scratch volumes must be explicitly requested through data class by the specification of MEDIA6, MEDIA8 MEDIA10, or MEDIA12. In the MTL environment, WORM scratch mounts can be managed through the tape management system pooling support instead of by data class. The DEVSUPxx PARMLIB member keyword, MTL_NO_DC_WORM_OK, allows a WORM scratch volume to be used even if it is not explicitly requested through data class.
Also see Logical WORM considerations.