1. When an index is deleted (dropped) from the Database Schema, the space in the index block will be reused. When an index entry is truly deleted, the object is deleted so the space that was previously used in the index blocks is added to the Free chain for that Storage Area and will be reused over time, by other objects in that Storage Area. Dropping an index is not always associated with deleting records.
2. When all the entries in an index block are deleted, but the index remains in the Database Schema, it will become a free block. This situation can arise from either deleting associated records or truncating the area where indexes are stored, leaving the index inactive.
When an index block becomes empty:
- In a Type II area the free block is put on the Free chain for the object
- In a Type I area the free block is placed on the Free chain for the area.
In a Type I area the blocks on the Free chain can be reused by other objects as well, i.e. records or other indexes.
In a Type II area, until the object is deleted, the space freed will only be reused by the same object. The blocks on the free chain will be reused if the index tree grows.
After large purge, it is advisable to run IDXCOMPACT to clean up the index delete chain.
After truncating an index area, the index should either be rebuilt or dropped from the Application Schema once the Primary Index has been rebuilt.
