The media Summary report will also give you a quick reference - pinning down when they were frozen from historical data wont be so easy (or possible most likeley as logs will probably only go back 30 days)
It would be better to setup monitoring or reporting (OpsCenter maybe or SCOM) to detect when this happens
On Windows it does get written to the event logs along with a reason
The Tape Reports and / or All Log Entries report will also have details - as will the bptm logs
It is worth digging into it if you get a lot frozen to find out the reason and get it resolved to make sure your non-frozen tapes really are good
Hope this helps
At the moment I select frozen tapes with a script and unfrreeze them. When the same tape is frozen thrice I move it to a "defect" pool. In a SAN environment with shared drives tapes are frozen without having a media problem - which is unusual anyway with TS1130. But if it hits the same tape more than once the problem should be the media. I don't care what it is, I just don't use the tape anymore. This can easily be automated. Search the ID of an unfrozen tape in a file, if you find it more than your threshold move it to a special pool and delete the ID from the file. Otherwise write the ID to the file.
One thing to mention. You should always investigate frozen media. When you unfreeze a tape, remember that it will be used. I have seen an scenario where someone unfreeze a tape that had been set to freeze for legal reasons. In that scenario the tape was overwritten. I users that if you need to keep a tape, you should vault it off or write protect the tape or set it to suspend. If you just leave it as frozen, someone else may unfreeze it .
You may be increasing your workload if you unfreeze all of your tapes. They were frozen for a reason and you should determine what that reason was before unfreezing the tape and placing it into scratch pool for reuse. A single bad tape can monopolize a tape drive for an entire weekend and jeopardize your success in meeting your site's backup window.
DOCUMENTATION: How to troubleshoot frozen media on UNIX and Windows
.Any tape that is frozen on purpose should be moved to a volume group other than the library and possibly sent offsite for safe storage. Do not leave them in the library as barcode labels have been known to come off a cartridge.
If you have a solaris server to hand, have a look at tperr.sh script.