We will be upgrading tape drives in one of the IBM tape libraries to newer, higher capacity models.  

While we will try to keep the tape library online during this upgrade (in order to keep it transparent as much as possible), there will be some periods where the library will be inaccessible. During these periods, CASTOR read requests to tapes in this library will be delayed; writing to CASTOR will not be affected as write requests will be transparently redirected to other libraries.  

To check if a given file will potentially be affected you can use the command:  
'nsls -T /castor/cern.ch/.../filename'   to find out the tape volume name (3rd column) and  
'vmgrlistatape -V tapename'   to retrieve the library name (3rd column).

If the library name is 'IBM_LIB3' your file _might_ be affected by the intervention.