In order to keep track of available volumes and files, OpenInsight maintains two system "files" -- SYSVOLUMES and SYSTABLES. As their names imply, these files contain information about currently available volumes and tables (files), respectively.
In fact, these files are simply system variables (@VOLUMES for data in SYSVOLUMES and @TABLES for data in SYSTABLES). However, to provide standard access to the information in these variables, they are accessible via the BFS RTP50 (memory resident files) as normal OpenInsight files. Because they are not true files, they cannot be updated by users.
Information in the SYSVOLUMES and SYSTABLES files is maintained by processes such as Attach_Table, Create_Table, Delete_Table, and others. For example, the Attach_Table process builds a SYSVOLUMES file entry for the volume being attached, and creates a series of SYSTABLES entries, one for each file being attached.
The SYSTABLES File
Each file that is attached has an entry in the SYSTABLES file and stored in the @TABLES array. The field layout of these entries is:
Field Number | Description |
0 (key) | File Name. The name by which a user accesses the file |
1 | Volume name. The volume from which this file was attached. This is the volume name as found as an entry in the SYSVOLUMES file. |
2 | True file name. This is different from the key only if this is an aliased table, as set by Alias_Table(). |
3 | Application. The application name to which this file belongs. |
4 | Filing System(s). The MFS/BFS list for that volume (delimited with @VM). |
5 | File Handle. If the file has been opened during this session, the file handle is stored in this field. If the file has not been opened, the next BASIC+ OPEN statement will generate a filing system OPEN.FILE call. |
