Too many tape errors

We do our nightly backup to a 3570 tape drive.  Friday night we had a media
error.  On Monday I did a PRTERRLOG TYPE(*VOLSTAT) VOLTYPE(3570) and got
the following for the tape:

Volume        --Temporary Error--   ----Perm Error-----   ------K
Bytes------
ID                Read      Write       Read      Write       Read
Written
160C65               0        102         23          4       5503
193791669

It appears that this tape should have been retired.  Last night we got a
media error on a different tape.  I did the PRTERRORLOG on it this morning
and got:

Volume        --Temporary Error--   ----Perm Error-----   ------K
Bytes------
ID                Read      Write       Read      Write       Read
Written
304748               0          1          0          0        240
194211057

This tape only had one error against it.  Is there a rule of thumb as to
when tapes should be trashed?  Is one error too many?  It is my
understanding that the drive is supposed to automatically clean itself
although I manually took the option to clean it a couple of weeks ago.  Any
ideas?


Dave Parnin
Nishikawa Standard Company
Topeka, IN  46571
daparnin@xxxxxxxxxxxxxx