If write access to a tape file is permitted, all subsequent files on this tape are implicitly deleted, regardless of their protection attributes. Their catalog entries remain unchanged, but the data can no longer be accessed.
If the FILE macro with the operand SECLEV=(...,OPR) or the ADD-FILE-LINK command with the operand OVERWRITE-PROTECTION=YES is executed, the system checks, during a write access, which protection attributes have been specified for the new file. If this new file is not the first file on the tape, its protection attributes are compared with those of the immediately preceding file on the tape.
An attempt to write to the tape is rejected if
ACCESS=READ is specified for the current file and ACCESS=WRITE is specified for the immediately preceding file or
the retention period specified for the current file is greater than that for the immediately preceding file.
As a result of this, the protection specified for the first (or immediately preceding) file on the tape determines whether or not the following files are protected against overwriting.