The SYSTABLES table is keyed by the name of the table (as you would pass it to the BASIC+ OPEN statement) and contains five fields:

  1. The key to the SYSVOLUMES table for the volume that contains this table name;

  2. The name by which the volume knows this table (i.e. the name that this table is listed as in the volume’s media map);

  3. The database name that owns this table, or GLOBAL if this table is meant to be available to all applications;

  4. The name of the filing system function (or an @vm-delimited list of functions, when one or more MFSs are used) that implements access to this table;

  5. The information that the filing system function(s) need to access this particular table, or blank if this table has not been opened; this field is called the “handle”.

The SYSVOLUMES table has a two-part key in OpenInsight:

  1. The base filing system that implements access to the volume;

  2. The name of the volume, which may be a path name in the case of directory-based implementations such as Linear Hash;

The SYSVOLUMES table contains six fields:

  1. A volume stamp (or label) which is intended to uniquely identify a volume even if two different volume names (for example, two mapped drives that refer to the same directory) refer to the same volume;

  2. Generally referred to as the volume’s location, this field contains information that the filing system function needs to access the media map (and perhaps the tables too);

  3. The list of tables (@vm-delimited) from this volume that are in SYSTABLES; note that each of the referenced tables will have this volume’s key in the first field of their SYSTABLES records;

  4. The name of the filing system function (or an @vm-delimited list of functions, when one or more MFSs are used) that implements access to the volume’s media map;

  5. The information that the filing system function(s) need to access the media map; this field is called the handle;

  6. This field is used for control information; this was added either for the VMARK or SQL Server bond, so chances are you will never see anything in field 6.

If you look at the SYSTABLES information for the tables named SYSTABLES and SYSVOLUMES, you will see that the filing system is RTP50 and the handles (field 5) are T and V.  RTP50 is a filing system function that presents the information as if it were a table called SYSTABLES, and it presents the information in as if it were a table called SYSVOLUMES.

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