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# Optimizing Drupal database usage

> Drupal's caching and logging features can cause the database to grow large and slow site performance. Learn how to optimize Drupal database usage.

This article discusses how to optimize Drupal database usage and help prevent databases from becoming too large.

## Database usage in Drupal

Drupal's caching and logging features can cause the database to grow very large, particularly when a site uses the default configuration settings. When the database becomes too large, site and server performance can be affected.

<Note>
  For information about how to determine the size of a MySQL database or its tables, please see [this article](/docs/determining-the-size-of-mysql-databases-and-tables).
</Note>

You can optimize Drupal's database usage and improve site performance by:

* Configuring Drupal's cron routine. Drupal's cron routine checks for system updates, maintains database logging information, and more.
  > 🚧 Important
  >
  > If you have not already set up Drupal's cron routine, please see [this article](/docs/configuring-the-drupal-cron-routine) for information about how to do so.

* Clearing Drupal's caches. You can do this manually, and you can also set up a dedicated cron job so caches are cleared automatically. This article demonstrates how to do this.

* Configuring how much information Drupal's database logging ( **dblog** ) module stores in the database. This article explains how to do this.

## Clearing the cache manually

Drupal maintains multiple caches, and over time they can grow quite large. When this occurs, your site's performance can decline.

You can manually clear Drupal's caches using the administration interface or the [Drush command-line tool](http://www.drush.org/). Use whichever method you prefer:

### Method#1: Using the Drupal administration interface

* To clear all caches in Drupal 6 using the administration interface, follow these steps:

  1. Log in to Drupal.

  2. In the left pane, click **Administer**, and then click **Site configuration**.

  3. Click **Performance**.

  4. Scroll down the page, and then click **Clear cached data**.

* To clear all caches in Drupal 7 using the administration interface, follow these steps:

  1. Log in to Drupal.

  2. On the top menu bar, click **Configuration**.

  3. Under **DEVELOPMENT**, click **Performance**.

  4. Click **Clear all caches**.

### Method #2: Using Drush

To clear Drupal's caches from the command line using Drush, follow these steps:

1. Log in to your account [using SSH](/docs/using-ssh-secure-shell).

2. At the command prompt, change to the directory where Drupal is installed. For example, type `cd ~/public_html`.

3. Type the following command:

```bash theme={null}
drush cache-clear all
```

## Configuring a cron job to clear the cache automatically

The previous section explains how to clear Drupal's caches manually. A more long-term solution to keeping the database size manageable, however, is to set up a cron job that clears Drupal's caches at fixed intervals. (This cron job only clears the caches, and is separate from the [Drupal cron routine in thecron.phpfile](/docs/configuring-the-drupal-cron-routine).)

You can set up this cron job from the command line, or use cPanel. Use whichever method you prefer:

### Method #1: Using the command line

To use the command line to set up a cron job that clears the caches, follow these steps:

1. Log in to your account using SSH.

2. At the command prompt, type the following command to access the cron configuration file:

```bash theme={null}
crontab -e
```

3. To enter insert mode, type `i`.

4. Add the following lines to the cron configuration file. You can change the date and time to whatever you want:

```
## Clear the cache once a week at 2:30 in the morning on Sunday:
30 02 * * Sun     cd ${HOME}/public_html; drush cache-clear all >/dev/null 2>&1
```

<Note>
  * You can modify the cron job intervals to clear the cache more frequently if you want. For example, if you have a busy Drupal site, you may want to clear the caches more than once a week.

  * If you installed Drupal in a subdirectory beneath the *public\_html* directory, modify the **cd** command to change to that directory instead.
</Note>

5. To save your changes and exit the editor, press ESC, type `:wq` and then press Enter. You see the following message:

```
crontab: installing new crontab
```

6. To verify the cron configuration, type the following command:

```bash theme={null}
crontab -l
```

### Method #2: Using cPanel

To use cPanel to set up a cron job that clears the caches, all you need to do is specify the interval (for example, weekly, monthly, etc.) and the command to run.

To clear Drupal's caches using Drush, specify the following command:

```bash theme={null}
cd ${HOME}/public_html; drush cache-clear all >/dev/null 2>&1
```

<Note>
  If you installed Drupal in a subdirectory beneath the *public\_html* directory, modify the\
  **cd** command to change to that directory instead.
</Note>

For detailed information about how to set up a cron job using cPanel, please see [this article](/docs/cron-jobs).

## Configuring the database logging (dblog) module

The database logging (**dblog** ) module saves system events in the database. These events include usage and performance data, errors, warnings, and operational information.

You should view the dblog report periodically to make sure your site is running normally. Additionally, you should optimize the dblog module settings to prevent the database from growing too large.

<Warning>
  **Important**

  If you have not configured Drupal's cron routine, you should do so before following the procedures below. Otherwise, the following settings will have no effect. (Drupal's cron routine performs many routine maintenance tasks and is separate from the cron job described in the previous section for clearing the cache.) For information about how to set up Drupal's cron routine, please see [this article](/docs/configuring-the-drupal-cron-routine).
</Warning>

### Drupal 6

To view the dblog report on Drupal 6, follow these steps:

1. Log in to Drupal.

2. In the left pane, click **Administer**, and then click **Reports**.

3. Click **Recent log entries**. A list of recent log entries appears.

To configure the row limit for database logging, follow these steps:

1. In the left pane, click **Administer**, and then click **Site configuration**.

2. Click **Logging and alerts**, and then click **Database logging**.

3. In the list box, select **100**. This setting reduces the number of log entries (rows) to maintain, and helps control the database size.

4. Click **Save configuration**.

### Drupal 7

To view the dblog report on Drupal 7, follow these steps:

1. Log in to Drupal.

2. On the top menu bar, click **Reports**.

3. Click **Recent log messages**. A list of recent log entries appears.

To configure the row limit for database logging, follow these steps:

1. On the top menu bar, click **Configuration**.

2. Under **DEVELOPMENT**, click **Logging and errors**.

3. Under **Database log messages to keep**, select **100**. This setting reduces the number of log entries (rows) to maintain, and helps control the database size

4. Click **Save configuration**.

## Related articles

* [Using Drush for Drupal](/docs/using-drush-for-drupal)

* [Checking MySQL database and table sizes](/docs/determining-the-size-of-mysql-databases-and-tables)

* [Optimizing and repairing MySQL databases with phpMyAdmin](/docs/optimizing-and-repairing-mysql-databases-with-phpmyadmin)