I have found tapes that are not scratching because the OSC bit is turned on and the tape data set is no longer cataloged.
1. How does this happen?
2. How do I correct so the tapes can be scratched?
1. This can happen if a tape data set is uncataloged or a GDG was rolled off when CA 1 was not active. If the tapes are OLD it could have happened if you mixed the media of a GDG between DASD and tape and had the old option of MIXGDG set to NO. When you created the data set on DASD CA 1 did not check that the tape being rolled off was on tape so the OSC bit was not updated. MIXGDG was removed by PTF RO10164, rel 11.5 in 2009.
2. You can use TMSUPDTE to turn off the OSC bit on the volume record or TMSUDSNB for a DSNB record. Also take a look at the CTLGCNT and make sure it is also set to zero.