iAnywhere.com - Types of index

Types of index

Adaptive Server Anywhere supports two types of index, and automatically chooses between them depending on the declared width of the indexed columns. For a total column width that is less than 10 bytes, Adaptive Server Anywhere uses a B-tree index that contains an order-preserving encoding, or hash value, that represents the indexed data. Hash B-tree indexes are also used when the index key length is longer than one-eighth of the page size for the database or 256 bytes (whichever is lower). For data values whose combined declared length is between these two bounds, Adaptive Server Anywhere uses a compressed B-tree index that stores each key in a compressed form.

Indexes can be stored as either clustered or unclustered. Clustered indexes may assist performance, but only one index on a table can be clustered.

Hash B-tree indexes
Compressed B-tree indexes
Recommended page sizes