MASTER FILE RECOVERY UTILITY

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This program will attempt to recover the Master file records without using
the XRF file. Before using the program it is advisable to take a DOS backup
of the Master file. The program will also work on a Master backup file
(extension .BKP).

At the DOS prompt, call the program as follows:

> MSTRCV2

You are then prompted to supply the name of the Master file to be recovered
and of the corresponding XRF file as follows:

MST: (reply to this prompt with the master file name, which must include the
     the full path and file extension, e.g. \ISIS\DATA\ABCD.MST)
XRF: (reply to this prompt with the crossreference file name to be recreated,
     e.g. \ISIS\DATA\ABCD.XRF)
Max MFN?  (reply to this prompt with the highest MFN you have enetered in the
          data base. This number need not be precise, but it must be high
          enough to cover the last entered record. For example if you think
          that the highest record was 985 but you are not sure, you may reply
          to this prompt with 1000, if you are sure that the last MFN created
          was lower than 1000. This number is used to perform one of the
          consistency tests described below.)

After you have responded to the three prompts described above the program
begins to read the master file sequentially and assumes that the records
are contiguous.

For each record processed the following information is displayed:

   b/o  MFN=n  LEN=rl  BWB=bb   BWP=bp

where:

   b      is the current block number
   o      is the offset in the block
   n      is the MFN of the record
   rl     is the record length
   bb     is the value of MFBWB
   bp     is the value of MFBWP


The following consistency checks are then performed to determine a possible
discontiguity:

a. The MFN must be positive and within the specified range
b. The record length must be positive, not less than 18 and not greater than
   the system supported maximum record length (currently 8000 bytes)
c. MFBWB and MFBWP must be positive or zero. If greater than 0 then
   MFBWB must be less or equal to the current block number and MFBWP must
   not be greater than 500

If all tests are satified, the program assumes that it is handling a record
and, using the current position and the record length tries to proceed to
the next record.

If any of the above tests fails the program will continue to scan the file
sequentially until a record is found.

This process is repeated until the whole file has been examined.

At this point you have the option of re-initializing the control record.  The
program will ask confirmation as follows:

  OK to reset MST control record (Y/N)?  (if you reply Y the master file control
                                 record is recreated by resetting NXTMFN to the
                                 highest MFN processed plus one, and NXTMFB and
                                 NXTMFP are set to point after tha last record
                                 in the file)

Note that if you use a backup file (.BKP) as input, you must rename it with
the correct master file extension .MST after the recovery.