Tapes have traditionally been managed by the expiration dates written in the tape labels. Standard IBM support for date- protected data sets requires operator intervention to rewrite a protected tape before its expiration date.
Note: For more information, see Year 2000 Considerations in the User Guide.
Tape management systems usually extend this support in several ways. They interpret certain expiration dates as codes to indicate the type of control governing the use of the tape. A master control file, or tape management catalog, records this information, and controls access to each tape. If the control file indicates a tape as an available scratch tape, it allows it to be rewritten without operator intervention, regardless of the expiration date in the label.
For example, CA 1 uses an EXPDT=99000 to mean that a tape is eligible as a scratch tape when it becomes uncataloged. As long as the tape is cataloged, it is protected from being used as a scratch tape. This is commonly known as catalog control. An EXPDT=99365 is often used as the code to mean permanently protected -- the tape cannot be reused as a scratch tape unless the control file is updated to change this status. If you are using LDATE/ddd (to retain ddd days after the tape was last used) be aware that CA 1assigns an expiration date of 98ddd, which might be confusing since it, shows as 1998ddd in some of our reports. Consult the documentation for your tape management system to find the various means of control it provides through expiration date codes.
IBM also recognizes 99365 as a never expire date. This means that for standard applications, operator intervention is required to rewrite such tapes. However, IBM has also provided an exit to allow operator intervention to be avoided. CA Disk optionally makes use of this exit, based upon the value of sysparm TAPEFSCR.
CA Disk uses standard techniques to open and write tape data sets, which causes tape labels and their expiration dates to be created by normal means. As distributed, CA Disk dynamically allocates all tapes that are needed and assigns them an expiration date of Julian 99365 (from the default value of sysparm DYNEXPDT). This value guarantees the integrity of the data by ensuring that a tape never expires before the data that it contains. CA Disk determines when all of the data on each tape has expired, and at that point returns it as an eligible scratch tape.
CA Disk also provides an option to catalog each tape data set that it creates. By specifying expiration dates and catalog options correctly, CA Disk is fully compatible with all major tape management systems. As mentioned above, sysparm DYNEXPDT controls the expiration date for dynamically allocated tapes. If you supply DD statements for the output tapes, the expiration date you supply in the JCL is used.
A description of several implementation options relating to tape management in general is presented in the Tapepool Considerations section in the Systems Guide. CA Disk provides three methods for controlling tapes. Select one of these methods and follow the instructions for installing the tape management support.
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