When using RDTAP to read and extract data from the archive tapes be aware that the newly created disk files are always placed in the users default directory. RDTAP has an on-line brief help information listing to aid the unfamiliar user. To activate this feature type RDTAP without any parameters at the IDL prompt. To get a listing of the contents of the tape one can either use the RDTAP utility with the option to extract the tape directory files IDL> rdtap, device, /dir which creates the two files called `xadyy_wkd.xx' (ASCII) and `xbdyy_wkd.xx' (binary). An alternative method is to simply copy the first file (the ASCII file) from the tape to disk via DCL or Unix commands (e.g. for VMS mount/for mt: and copy mt: tapedir.lis or for Unix cp dev tapedir.lis). When extracting the binary data files from tape to disk the files are restored without any byte swapping. This keeps the files in their original format so that any byte swapping, if necessary, is handled automatically and transparently to the user at the time the disk files are read by the analysis software. Note that the tape is rewound at the beginning of each RDTAP request, so it is more efficient to specify all requests within a single RDTAP command than it is to make several smaller requests. Also the requested list of the files need not be in order of appearance on the tape as the routine will sort all input requests for the most efficient extraction.
The general calling sequence for RDTAP is:
IDL> rdtap, dev [, file, prefix= prefix, fileID= fileID, week=week, $
IDL> dir=dir, range= range, software= software]Where the optional parameters are enclosed within brackets (note that
when calling RDTAP with the 
parameter specified at least one other
optional parameter must also be included. In general, all non-switch
parameter inputs have a string data-type (e.g. dev = `/dev/nrmt0h'). The
definitions of the parameters is as follows:
dev is the device name (Ultrix example: '/dev/nrmt0h').
file is a list of requested file names (e.g. spr910925.1020).
prefix is a list of requested file prefixes.
fileID is a list of requested fileIDs (e.g. 910925.1020).
week is a list of weekly files to restore.
dir is a switch to restore the tape directory file.
range is a switch to create a list of files from input.
soft* is a switch to restore the software tar file to disk.
Some examples are: IDL> rdtap, dev, ['spr911029.0300','bda911030.0440'] IDL> rdtap, dev, prefix=['spr','sfr'] or rdtap, dev, prefix=['s']IDL> rdtap, dev, fileID=['911029.0900']IDL> rdtap, dev, prefix='spr',fileID='910923.1234', week='all'IDL> rdtap, dev, prefix='s', fileid=['911101.0200','9111015.0900'],/rangeIDL> rdtap, def_tapd(1), /software, /dir The first example restores just the requested spr and bda files. The second example restores ALL SXT files from the tape (could take about two hours). The third example restores all archived files of this fileID. The fourth example restores just the spr910923.1234 file and all weekly files. Note, that week=[`obs', `pnt', `fem', `evn'] will restore any of these files found on the tape (i.e. if FEM and EVN files were missing, only OBS and PNT files would be restored. The fifth example restores sfr and spr files between orbits dated 1-Nov at 02:00 UT and 15-Nov at 09:00 UT. The last example decompresses the software archive file and restores the tape directory files to the default directory. Using the DEF_TAPD function to specify the device name by selecting the device number is a simple way to get the correct device name.
In using the tape directory file to review tape contents and select data files to be extracted from the tape, find the final table within the file which tabulates the fileID and file prefix. The heading of table reads FileID and cpio, followed by all of the valid file prefixes. To find a given file with the table, match the fileID with the corresponding row within the FileID column and then match the file prefix with the corresponding prefix column. A non-zero entry for the size of the file (bytes) indicates that the file is on the tape.