Ejabberd’s mnesia data base grew up to 2GB which gave me following error message in the logs:
`@mod_mam_mnesia:store:94 MAM archives too large, won't store message for ..@..`
This problem is already mentioned in the [documentation](https://docs.ejabberd.im/admin/configuration/#mod-mam). The solution is to switch the storage backend for mod_mam to mysql. This is straight forward as described in many tutorials and very easy. But I had one problem after creating the database and adding the information to the ejabberd configuration:
`@ejabberd:exit_or_halt:133 failed to start application 'p1_mysql'`
This means that that the erlang module for accessing mysql is missing. Installing `erlang-p1-mysql` solves the startup error. Make sure to stop ejabberd before the installation.
If your instance has not much traffic, it is possible that the connection to your mysql server will time out:
`@ejabberd_sql:log:910 p1_mysql_conn: Connection closed, exiting.`
There is a keep alive setting for ejabberd which prevents the timeout when set to 8 hour interval:
```
sql_keepalive_interval: 28800
```
You may consider to change the pool size for mysql connections to reduce memory consumption (default is 10):
```
sql_pool_size: 5
```