Gap4 does not store the trace data within the gap4 database. Instead it stores the filename of the trace file. Usually the trace files are kept within the same directory as the gap4 database. If this is not the case gap4 needs to know where they are.
To make sure that gap4 can still display the traces we need to specify any alternative locations where traces may be found. The "Trace File Location" command (which is available from the gap4 Options menu) performs this task. It brings up a dialogue asking for the directory names. If there is just one directory to specify, its name should be typed in. If there are several directories to search through, they must all be typed in, separated by the colon character (":"). To include a directory name that contains a colon, use a double colon.
For example, on windows to specify two directories, use (eg)
"F::\tfiles1:G::\tfiles2".
In addition to specifying directories, RAWDATA may also be used to indicate
that the trace files are contained within a tar file. The syntax for
RAWDATA is then TAR=filename. This can be combined with
directories if desired (for example,
.:/traces/online:TAR=/traces/archive.tar). In order to speed up
accessing of traces within the tar file a command line utility named
index_tar may be used. This produces a text index containing the
filenames held within the tar and their offsets within it. Programs will then
use this index file to provide a fast way of accessing the trace. The syntax
for index_tar is: index_tar tar_filename >
tar_filename.index. (For example "index_tar traces.tar >
traces.tar.index".)
If the gap4 database has been opened with write-access this directory
location will be stored as a database RAWD note
(see section Special Note Types), which is read by gap4 when
it opens the database. The demonstration data supplied with the package
includes an example database (named DEMO.0) that has a RAWD note to specify
that traces are fetched from a tar file within the same directory.
An alternative way of specifying the trace file location is by setting the
RAWDATA environment variable. On Unix and Windows NT this is
straightforward (although system and shell specific). However on Windows 95
this may prove difficult (and at least require a reboot), so manually setting
the environment variable is no longer recommended.