Restrictions

System catalogs, MOTs, global temporary tables, local temporary tables, sequence tables, Ustore segment-page tables, unlogged tables, and compressed TOAST data are not supported.
User can set ILM policies for ordinary tables, partitions, and level-2 partitions.
Astore/Ustore user tables of ordinary tables, partitions, and level-2 partitions are supported.
This feature is valid only in A-compatible, PG-compatible, or B-compatible mode.
Ustore does not support encoding and decoding, thus offering a compression ratio lower than Astore.
The partial decompression feature is added to the current version. As a result, some small tables are not compressed because their compression gain does not meet requirements. However, they can be compressed in earlier versions without the partial decompression feature. For example, a table containing only one column of the int1 type cannot be compressed since the current version.

Parent topic: Data Lifecycle Management: OLTP Table Compression