Creating a Compressed Index

To designate index compression for a index or local index partition level, use the index_compression clause.

Only leaf pages are compressed. Compressed and uncompressed index rows may coexist on a single index leaf page. If compression has not been specified anywhere in the table or index DDL, then the indexes are not compressed. APL-clustered indexes are not supported by index compression. Unique indexes that have only one column are not compressed.

Specifying compression at the index level overrides index compression specified at the table level. Local index partition level specification overrides the index-level specification.

Using the create index Command

The WITH index_compression clause provides these compression options:

NONE – the index page for the specified index is not compressed. Local index partitions that are specifically created with index_compression = PAGE are compressed.
PAGE – when the page is full, existing index rows are compressed using the page prefix compression. When a row is added, a check is performed to determine whether the row is suitable for compression.