The FATMEN file catalogue retains minimal information about tapes upon
which data reside. It assumes that full details are kept in a Tape
Management System (TMS), with which the file catalogue is fully
integrated. When a user wishes to access a dataset on a given tape or
cartridge, the FATMEN system will inquire of the TMS whether the user has
the required access permission, whether the media is in fact available,
its location etc. Using the information returned, it will then build a
valid tape STAGE request, specifying the device type required and other
details such as label type (ASCII, EBCDIC, Unlabelled). Thus, users need
not know that their data resides on a tape which is in an automatic
loader, or indeed if it is on tape at all!
When a new dataset is created, the TMS may also be used to allocate a new
tape or cartridge within a certain storage group as specified by the user.
The TMS provides a great deal of flexibility in this area, thus an
experimental group may divide up its tape allocation into separate pools
for raw data, Monte Carlo data, DSTs and other data. The user may then
request a tape from the appropriate storage pool, or provide a user
routine to perform the allocation.
The CERN TMS resides on CERNVM. All access to the TMS is via the SYSREQ
communications package. Remote access is provided via a TCP/IP server into
CERNVM, called TCPREQ. The user may issue TMS commands without passing
through the FATMEN system: these will typically be performed by the tape
librarian or group tape managers. More details of the TMS are given in a
separate document: The CERN Tape Management System (to be published).
Remote sites with their own TMS's are required to provide two FORTRAN
interface routines to link their TMS to the FATMEN system. An interface
already exists for VMTAPE and is selected with the PATCHY flag
+USE,VMTAPE.
The following restrictions apply if the FATMEN file catalogue is used
without a TMS:
- Default values are used for media types (e.g. 3480), generic device
types (e.g. CT1), label types (e.g. SL) etc. These may be changed at any
time by calling the routine FMEDIA.
- For individual tape volumes, this information can be overridden by
providing a user exit FMUTMS. This exit also permits the user to indicate
that a volume is inaccessible (unavailable or permission denied).
- To allocate volumes from named pools at run-time, a user-exit FMUALL
must be provided.