Run the four statements in the Ad Hoc command window to the right.
This step shows you how to compress existing tables.
The first statement creates a new table CUSTOMER_ADDRESS_WITH_COMPRESSION. All the rows from the original CUSTOMER_ADDRESS_WITHOUT_COMPRESSION table are selected and inserted in the new table. The two tables are identical in size.
The ALTER TABLE command switches on row compression for the CUSTOMER_ADDRESS_WITH_COMPRESSION table, but nothing is compressed until the final step.
The reorganization (REORG) command samples the table data, builds a compression dictionary and compress the data. After the REORG, any additional data inserted into the table is also compressed.