The DB_CONFIG File
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## The DB_CONFIG File

You can configure most aspects of your Berkeley DB environment by using the `DB_CONFIG` file. This file must be placed in your environment directory. When using the BDB SQL interface, this is the directory created alongside of your database. It has the same name as your database, followed by a `-journal` extension. For example, if your database is named `mydb.db`, then your environment directory is created next to the `mydb.db` file, and it is called `mydb.db-journal`.

If a `DB_CONFIG` file exists in your environment directory, it will be read for lines of the format NAME VALUE when your environment is opened. This happens when your application starts up and creates its first connection to the database.

One or more whitespace characters are used to delimit the two parts of the line, and trailing whitespace characters are discarded. All empty lines or lines whose first character is a whitespace or hash (#) character are ignored. Each line must specify both the NAME and the VALUE of the pair. The specific NAME VALUE pairs you can use with the BDB SQL interface are documented in DB_CONFIG Parameter Reference.

In some cases, you must either specify a configuration option before the environment is created, or the environment must be re-created before the configuration option will take effect. The documentation for each configuration option will indicate where this is true.

### Creating the DB_CONFIG File Before Environment Creation

In order to provide the `DB_CONFIG` file before the environment is first created, physically make the environment directory in the correct location in your filesystem (this is wherever you want to place your database file), and put the `DB_CONFIG` file there before you create your database.

### Re-creating the Environment

Some `DB_CONFIG` parameters require you to re-create your environment before they take effect. The `DB_CONFIG` parameter descriptions indicates where this is the case.

To re-create your environment:

- Make sure the `DB_CONFIG` file contains the following line:

      add_data_dir ..

  (This line should already be in the `DB_CONFIG` file.)

- Run the db_recover command line utility. If you run it from within your environment (`-journal`) directory, no command line arguments are required. If you run it from outside your environment directory, use the `-h` parameter to identify the location of the environment:

      db_recover -h /some/path/to/mydb.db-journal

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