ch bitmap page has its own ID
which are reserved in objects index. When database is created, DyBASE reserve in object index space for 
identifiers of ALL bitmap pages needed to map database virtual space (defined by <code>dbDatabaseOffsetBits</code>).
Number of bitmap pages needed to map the whole database can be calculated as <code>2 ** (dbDatabaseOffsetBits-32))</code>.
Actually index will be two times larger, because it should contain some other elements and when index is reallocated its
size is always d