Database File Access

The sub base level is not supported anymore in the database but still appears in database header definitions, i.e. only one sub base (sub base 0) is defined for each main base.

Base header properties are defined in corresponding database headers inheriting from each other. Thus, an EB_extRBHeader (rootbase header) is a main base header (EB_extMBHeader) which defines main base 0, but may also refer to a number of additional main bases.A main base header is a sub base header (EB_extSBHeader), which defines the only one sub base for a main base. A sub base header, again, is a data area header ()EB_extDAHeader), defining the data area 0.

Finally, each data area header is an external database header (EB_extHeader), which defines the current header length, which depends on the header type.

The root base header is located always at the beginning of the database file (position 0).

Each header is extended with a corresponding header extension (EBRootBase, EBMainBase, EBSubBase, EBDataArea), which points to the file position for the next external header. Thus, one may dynamically add new main bases or data areas.