HCC in Exadata Database 11g

Oracle’s Hybrid Columnar Compression technology is a new method for organizing data within a database block. Storing  data in a ‘columnar’ format, where data is organized and stored by column. Otherwise row format is followed to store where all column data for a particular row is stored sequentially within a single database block.

Hybrid Columnar Compression: HCC  is a compression option available only for tables residing on Exadata Storage. 

Apart from Exadata storage, Axiom, the SPARC Super Cluster and the Sun ZFS Storage Appliance have the same technology. 

This won’t work on any other system as seen below:

SQL> alter table mine move compress for query high;

alter table mine move compress for query high

            *

ERROR at line 1:

ORA-64307: hybrid columnar compression is not supported for table spaces on this storage type

HIGH and LOW are the Options available in the above querry.

The above query was run on a non-exadata storage system.

HCC re-organizes data into Compression Units (CU). It comes in two forms; 

Warehouse Compression (add COMPRESS FOR QUERY to your table definition script)

 and Archive Compression (add COMPRESS FOR ARCHIVE to your table script).

Physical IO’s are reduced hence enhancing performance.