A provisional system of dumps and restarts for the filing system is now in operation. This is the only system at present available which provides continuity from one day to the next. It is consistent with the description of magnetic tape dumping given in Planning Document No. 14. Files with class P, W and A are preserved by dumping on magnetic tape shortly after they are created but users should note that temporary files with class T (the default setting) are not dumped.

A cycle of 3 magnetic tapes (10DP), 11DP and 12DP are used for dumping. The system fills one tape before moving to the next. The output for one period of activity is automatically written on unused tape - the system will refuse to overwrite dump information. A dump tape must be 'cleaned' before it can be used a second time. For the time being, a copy of the latest file directory and the name of the current dump tape will be kept in Room 11A.

To operate the system.

Find a paper tape called DUMP F.M.

Find out the name of the current dump tape

Load the current dump tape on deck n and tell the supervisor "tape on deck n is (DUMP)"

(a) To restart

Load paper tape at point marked 'LOAD FROM DUMP'

(b) To start dumping

Load paper tape at point marked 'CONTINUE DUMPING'

(c) To stop the system

Load paper tape at point marked 'PRINT AND STOP'

When the directories have been printed out kill the file master. DO NOT KILL THE DUMP PROGRAM it will kill itself. File the directory printout in Room 11A.


  1. Restart first loads the directories then the files.

    User can use the system after the directories have been recovered.

    Fault 204 is produced if the system is used before the directories are recovered.

    Fault 202 is produced if attempting to use a file before it is recovered.

    Fault 200 is produced if attempting to use a file while it is being recovered.

  2. 'Print and Stop' prevents all further filing action except closing a file and dumping. It then waits about 1½ minutes to allow the system to settle before printing the directories. Fault 204 is produced if the file master is used during this period.
  3. The system should be able to recover from an abrupt cessation of operations but it is always safer to kill the file master and allow the dump program to terminate itself naturally.

Copyright © circa 1966 University of Cambridge Computer Laboratory. Distributed by permission. Thanks to Barry Landy, Roger Needham and David Hartley for giving permission to distribute these documents. Thanks to Barry Landy for lending me the paper document from which this was scanned. Any typographical errors probably arose in the course of OCR.

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