Table Cache Option Oracle Tips by Burleson Consulting

The Data Warehouse Development Life Cycle

Oracle Features for the Data Warehouse

Turning on the table cache option

There are two ways to activate the table CACHE option. The option can be specified permanently with a CREATE TABLE or ALTER TABLE command, or a cache hint can be used with the cost-based SQL optimizer to direct the data blocks. A create and alter table example is shown below:

create table customer
storage (next . . . )
cache;
alter table orders cache;

Another method of invoking table caching can be done by adding CACHE hints. The CACHE hint is generally used in conjunction with the FULL hint to insure that a full-table scan is being performed against the target table. In the following example, a reference table called ZIP_CODE is cached into the buffer.

Select /*+ FULL(ZIP_CODE) CACHE(ZIP_CODE) */
zip_code, city_name, county_name, state_name
from ZIP_CODE;

The main purpose of the CACHE option is to allow small tables that are always read from front to back to remain in the data buffer. These types of table might include small reference tables or any tables that are intended to be read by using a full-table scan. Remember, the CACHE option requires:

---

This is an excerpt from "High Performance Data Warehousing", copyright 1997.

If you like Oracle tuning, you may enjoy the book Oracle Tuning: The Definitive Reference , with over 900 pages of BC's favorite tuning tips & scripts.  You can buy it directly from the publisher and save 30%, and get instant access to the code depot of Oracle tuning scripts.