This command places sets of 100 numerically sequential Virtual Volumes or individual Virtual Volumes in read-only mode so they cannot be overwritten or reused as scratch tapes.
Separate CA Vtape Complexes can be allowed to read each other's Virtual Volumes by adding one complex's Virtual Volume range to the other complex's Global VCAT and by sharing the ICF catalogs that contain the Externalized Virtual Volume catalog entries. By write-protecting the Virtual Volume range used by complex A in complex B's Global VCAT and vice versa, each complex can read the other complex's Virtual Volumes, but cannot overwrite them.
If complex B was allowed to overwrite the Virtual Volumes written by complex A, complex A would have no way of knowing that the Virtual Volumes had been changed. This type of action could cause data loss.
If two separate CA Vtape complexes need to share Virtual Volumes on an ongoing basis, the two complexes should be merged into one complex with a common DASD buffer and Tape Management System.
This command is also used to prevent the accidental overwriting of a critical Virtual Volume during problem determination. It is not used to extend the expiration date of a Virtual Volume. Virtual Volume expiration is controlled by the Tape Management System; consequently, the Tape Management System should always be updated to extend the expiration date of any Virtual Volume.
After Virtual Volumes are write-protected on their owning system, they must have write protection turned off before they can be reused as scratch tapes.
SVTn SET WRITPROT {ON | OFF},{VVE=volser | VVP=cccc00}
Where volser is the Virtual Volume VOLSER or cccc is the first four digits of the set of 100 numerically sequential Virtual Volumes to be processed (cccc00-cccc99).
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