The model Magento uses to store customer and product data results in longer than average SQL queries and more reads. Enabling the Flat Catalog option for Categories and Products will merge product data into one table, therefore improving performance.
Login to your administration area and go to – System > Configuration > Catalog Under “Frontend”, change “Use Flat Catalog Category” to yes. Under “Frontend”, change “Use Flat Catalog Product” to yes – this is optional. Next, you will want to clear your Magento cache. Finally, you will need to reindex the tables. Enable Compilation
[box type=”alert” border=”full”]Note: This can sometimes break some applications. After performing the following steps, please ensure that the site still performs as it did before enabling this feature.[/box]
Login to your administration area and go to – System > Tools > Compilation
Next, simply click the Run Compilation Process Button
After the compilation has run, it should enable itself automatically