How do tape volumes get read / write errors - please explain

[kpovenz]

Looking for some answers......

I would like to know how/why TSM labels a tape with read /write errors. What has to happen for this error to be put on a tape volume.

Also I would like to know how/why tapes are marked as reado/unavailable. What has to happen before these are put to reado/unavailable.

If you have any documentation that you can point to that states the reason why tape volumes are put into these states...please share the link.

Thanks for your help in advance.

Kevin

 

[moon-buddy]

Short answers (and not to be taken as etched-in-stone answers!):

1. Read/write errors can be caused by tapes getting bad. Tape drives or the application does a CRC (Cyclic-Redundancy-Check) and if the incoming data does not match (in write mode) what was written, the tape is marked bad for write. On read, tape drives or the application checks for a check sum or runs an algorithm. If the check sum or algorithm does not match what the meta-data says it should, the tape is marked bad for read.

2. ReadOnly is a mainly a function that can be used by any backup application, or in this case, TSM. One possibility: if there are so many bad writes but data can be read, the tape can be marked readonly. Unavailable means that the tape is not physically within TSM's reach so it is marked unavailable, i.e., outside of the library.

Do a GOOGLE search and you should see a lot of postings or discussions on these topics.

 

[kpovenz]

thanks for the quick response - I have been on GOOGLE searching but not really finding what causes these errors. You can find out how to fix the errors but not what caused them.

So thanks again.

 

[mike9686]

Check below link for tape error : http://www-01.ibm.com/support/docview.wss?uid=swg21259460