Access to data step by step

The following examples go through some of the various options available when accessing a dataset. The simplest example as already been given, and is access to a dataset using the FATMEN shell.

We just type 

FM> find generic-name unit

If unit is numeric, it will be interpreted as a FORTRAN unit number. Thus, after typing 

find //cern/cndiv/jamie/test 11

we would have the following.

  1. On VM systems, a FILEDEF on unit FT11F001 pointing to the dataset referenced by //cern/cndiv/jamie. Any mini-disk links and accesses or stage operations would have been performed automatically, so that a subsequent FORTRAN program could just open unit 11 and read.
  2. On VMS systems, a logical name FOR011. Once again, our FORTRAN program can just open unit 11 and read.
  3. On Unix systems, a soft link fort.11.

    One could also specify a unit such as VM11F001, if the file were to be read by VMIO, or any character string that would be used as a logical name or symbolic link, e.g. 

    find //cern/cndiv/jamie/test mydat

    Our FORTRAN program could then open the named file MYDAT. (On VM or MVS systems, this corresponds to the DDNAME, rather than the file name.)

    Normally, we will wish to issue the FIND command from FORTRAN, as this is more powerful. Although a routine FMFIND exists, we will describe the FMOPEN routine, which includes all of the functionality of FMFIND and more.

    Our call to FMOPEN looks like 

          CALL FMOPEN('//CERN/CNDIV/JAMIE/TEST',CHLUN,LBANK,CHOPT,IRC)

    Here, the generic name and unit are specified exactly as in the shell, and are both of type character. This permits the use of units such as VM11F001, MYDAT and so on. Again, if we call FMOPEN with 

          CALL FMOPEN('//CERN/CNDIV/JAMIE/TEST','11',LBANK,CHOPT,IRC)

    the correct FORTRAN name on the system in question would be used. The exception to this is when the generic name in question points to a file which should not be processed by FORTRAN. In this case, FMOPEN will automatically perform the correct operation. For example, EPIO files on the IBM should be read with IOPACK, hence FMOPEN will build a DDNAME of IOFILE11. (This was also true for Zebra exchange format files on the IBM prior to version 3.67, when FORTRAN I/O became the default).

    Unlike the shell, FMOPEN will not only perform operations such as staging the file as required, but will also issue the correct OPEN. This may be overridden by the character option parameter CHOPT.

    FMOPEN options

    In the case of files to be processed by the Zebra FZ or RZ package, we can ask FMOPEN to perform the FZFILE or RZFILE call. For example, 

          CALL FMOPEN('//CERN/CNDIV/JAMIE/TEST','11',LBANK,'F',IRC)

    where F indicates that a call to FZFILE is to be issued. FATMEN obtains the correct parameters for the call to FZFILE from the catalogue.

    Another interesting option is the S option. This will instruct FATMEN to update the catalogue with the file size. This is useful for tape files, as future accesses will request a staging disk of the correct size, and hence use the system more efficiently.

    We can also request that an automatic duplicate of the file is made into the robot at CERN (SMCF), via the D option. This option requires a pool of tapes ggFAT1, e.g. XX-FAT1, in the TMS. Naturally, if a robot copy already exists a new one will not be made.

    Access to tape data

    For a dataset on a tape volume to be accessible, a device capable of reading or writing the volume must exist on the local node, or on a server node, in the case of remote access to data or VAXcluster systems.

    Suppose we wished to read the dataset with generic name //CERN/CNDIV/JAMIE/TEST. A copy of this dataset might exist on tape volume 123456. If this volume required a device of tape CT1, the FATMEN software will attempt to determine if such a device exists on the local node. Where remote tape access is available, it will check if such a device exists on one of the server nodes. This is done as follows.

    VM/CMS systems running HEPVM software

    A entry must exist in the file SETUP NAMES for the device CT1 (in this example). (Not yet implemented)

    VAX/VMS systems running VAXTAP software

    A logical name in the system table SETUPCT1S (in this example) must exist for locally attached tapes. Served tapes must be defined in the file SETUPEXE:TPSERV.CONF

    Cray Unicos systems

    An entry for the corresponding device must exist in the file /etc/shift.conf.

    Unix systems running the SHIFT tape software

    An entry for the corresponding device must exist in the file /etc/shift.conf or in the file /etc/TPCONFIG.

    Access to remote data

    The above examples will work on both local and remote data, without any change. Note that a call to FMOPEN on an Apollo in Helsinki will not result in a cartridge being mounted in the robot at CERN. Remote access to tape data must be explicitly enabled. It is currently enabled in the SHIFT facility, where the data is staged via the CRAY, and on the L3 Apollos, where the data is staged through LEPICS.

    Access to remote disk data requires explicit selection of a copy of a dataset. This may be done as shown below. 

                    Example of using the  FMSELK routine
                                  

    *     Argument declarations
      PARAMETER (LKEYFA=10)
      PARAMETER (MAXKEY=999)
      DIMENSION INKEYS(LKEYFA),OUKEYS(LKEYFA,MAXKEY)
*     The following statements will select all datasets
*     with copy level (MKCLFA) of 1 (i.e. a copy of an original file),
*     media type of 1 (i.e. disk) and location code of 1 (i.e. CERN)
      INKEYS(MKCLFA) = 1
      INKEYS(MKMTFA) = 1
      INKEYS(MKLCFA) = 1
      CALL FMSELK('//CERN/CNDIV/JAMIE/TEST',INKEYS,OUKEYS,NFOUND,MAXKEY,IRC)
      IF(NFOUND.GT.0) THEN
*     Just take the first one found which matches
         CALL FMGETK('//CERN/CNDIV/JAMIE/TEST',LBANK,OUKEYS(1,1),IRC)
*     Now pass the bank to FMOPEN.
         CALL FMOPEN('//CERN/CNDIV/JAMIE/TEST','11',LBANK,'F',IRC)
      ENDIF

    In the current version this dataset would only be accessible if mounted via NFS.