The SdU (SMARTdata Utilities) file system
supports sequential, indexed, and relative files.
When you create
an SdU file using
OPEN
OUTPUT and
WRITE statements, multiple files
are created:
- The file attributes are stored in files that have suffix .DDMEA.
- The primary index is stored in a file whose name begins with the
character @, followed by the file name.
- The alternate indexes are stored in files whose names end with
suffix .@00, .@01,
and so forth.
Because SdU files consist of multiple files that refer
to one another internally, do not attempt to copy, move, or rename
them. When you delete an SdU file (using the
rm command),
be sure to also delete all its component files, some of which are
hidden due to their having names that begin with a period (
.).
To list all the components of an SdU file named
Log123 in
the current directory for example, use the following command:
ls -l *Log123* .*Log123*
The SdU file system conforms
to 85 COBOL Standard.
Restrictions: - SdU files must not be accessed other than from COBOL
or PL/I programs, because the metadata for SdU files is stored separately
from the files (as described above).
- The SdU file system is not safe for use with
multiple threads.