Compressing data

Compress data in tables, indexes, and fragments to reduce the amount of needed disk space.

Prerequisites: For the space optimization actions, the HCL OpenAdmin Tool (OAT) for Informix® requires HCL Informix 11.50.xC6 or later. For the defragment action, OAT requires Informix 11.70 or later. To compress indexes and simple large objects (TEXT and BYTE data types), OAT requires Informix 12.10.

Important: The table or table fragment must contain at least 2000 rows. For an index or index fragment, the table that the index or index fragment is based on must contain at least 2000 rows. Detached B-tree indexes, including unique, duplicate, and forest of trees indexes, can be compressed.

When you compress a table, index, or fragment, the compression task creates a compression dictionary and compresses the data in the rows without moving them. When you compress tables, you can include the simple large objects (TEXT and BYTE data types) that are stored in partitions in the same dbspace. As part of the compression task, you can consolidate free space (repack) and return free space to the dbspace (shrink). You can also reduce the number of extents (defragment).

To compress tables, indexes, and fragments:

On the OAT menu, click Space Administration > Storage.
With the database server selected, expand the Tables and Indexes panel.
Select the tables, indexes, and fragments.
Click Actions > Optimize Space.
Select Compress.
Optional: Select additional actions:
- To consolidate free space, select Repack.
- To return any free space to the dbspace, select Shrink.
- To reduce the number of extents, select Defragment extents.

To monitor the progress of the task, click the Task Status tab.