Global allocation map pages

Each database has a Global Allocation Map Pages (GAM). It stores a bitmap for all allocation units of a database, with 1 bit per allocation unit. When an allocation unit has no free extents available to store objects, its corresponding bit in the GAM is set to 1.

This mechanism expedites allocating new space for objects. Users cannot view the GAM page; it appears in the system catalogs as the sysgams table.