GEOS SDK TechDocs|
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2 Database Structure | 
2.2 DB Groups The basic unit of data is the item . Items are simply chunks in special LMem heaps which are managed by the DB Manager; these heaps are called item blocks . You will not need to use any of the LMem routines; the DB manager will create and destroy LMem heaps as necessary and will call the appropriate routines to lock DB items when needed.
Each DB item in a DB file is uniquely identified by the combination of a group-handle and an item-handle . Note that these handles are not the same as the item's LMem Heap handle and its chunk handle. You will not generally need to use the item's heap and chunk handles; the DB routines store and use these automatically. However, you can retrieve them if necessary (for example, if you want to use an LMem utility on a DB item).
The DB Manager does not keep track of allocated items. Once you allocate an item, you must store the group- and item-handles. If you lose them, the item will remain in the file, but you will not be able to find it again.
Since DB items are chunks, their addresses are somewhat volatile. If you allocate an item in a group, other items in that group may move even if they are locked. (See the Local Memory chapter.)
GEOS SDK TechDocs|
| 2 Database Structure | 2.2 DB Groups