SDB_PhysicalMainBase - Physical main base definition

A physical main base definition is required, when a main base is supposed to consist of more than one data area or when the root base contains several main bases (maximum 4094). Main bases are using aconsecutive number starting with 0. Main base 0 is the default main base defined for the root base.

When no main base is defined in a database schema, main base 0 with a dynamic data area 0 will be created when creating a root base for a new database.

Main base numbers are stored in 16 high order bytes of the database entry number (LOID). The 4 high order bits are reserved for main base type identification High and low number define the range of valid main base numbers within an LOID. Usually, the values for low and high are identical with the main base number, since the lower 48 bit for numbering database entries within a main base are sufficient for most main bases.

A physical schema can be defined using main base definitions in the main base extent (SDB_MainBase). Additional physical schemata might be defined by means of root base definitions (SDB_RootBase).