======================
Database Configuration
======================

ownCloud requires a database in which administrative data is stored. The following databases are currently supported:

* :ref:`MySQL / MariaDB <db-binlog-label>`
* :ref:`PostgreSQL <db-postgresql-label>`
* :ref:`Oracle <db-oracle-database-setup>` (ownCloud Enterprise edition only)

The MySQL or MariaDB databases are the recommended database engines.

Requirements
------------

Choosing to use MySQL / MariaDB, PostgreSQL, or Oracle (ownCloud Enterprise 
edition only) as your database requires that you install and set up the server 
software first. 
(Oracle users, see :doc:`../../enterprise/installation/oracle_db_configuration`.)

.. note:: The steps for configuring a third party database are beyond the scope of this document.  Please refer to the documentation for your specific database choice for instructions.

.. _db-binlog-label:

MySQL / MariaDB with Binary Logging Enabled
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

ownCloud is currently using a ``TRANSACTION_READ_COMMITTED`` transaction isolation
to avoid data loss under high load scenarios (e.g., by using the sync client with
many clients/users and many parallel operations). This requires a disabled or
correctly configured binary logging when using MySQL or MariaDB. Your system is
affected if you see the following in your log file during the installation or
update of ownCloud:

 An unhandled exception has been thrown:
 exception 'PDOException' with message 'SQLSTATE[HY000]: General error: 1665 
 Cannot execute statement: impossible to write to binary log since 
 BINLOG_FORMAT = STATEMENT and at least one table uses a storage engine limited 
 to row-based logging. InnoDB is limited to row-logging when transaction 
 isolation level is READ COMMITTED or READ UNCOMMITTED.'

There are two solutions. One is to disable binary logging. Binary logging 
records all changes to your database, and how long each change took. The 
purpose of binary logging is to enable replication and to support backup 
operations.

The other is to change the BINLOG_FORMAT = STATEMENT in your database 
configuration file, or possibly in your database startup script, to 
BINLOG_FORMAT = MIXED or BINLOG_FORMAT = ROW. See `Overview of the Binary 
Log <https://mariadb.com/kb/en/mariadb/overview-of-the-binary-log/>`_ and `The 
Binary Log <https://dev.mysql.com/doc/refman/5.6/en/binary-log.html>`_ for 
detailed information.

.. _db-transaction-label:

MySQL / MariaDB "READ COMMITED" transaction isolation level
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

As discussed above ownCloud is using the ``TRANSACTION_READ_COMMITTED`` transaction isolation
level. Some database configurations are enforcing other transaction isolation levels. To avoid
data loss under high load scenarios (e.g., by using the sync client with many clients/users and
many parallel operations) you need to configure the transaction isolation level accordingly.
Please refer to the `MySQL manual <https://dev.mysql.com/doc/refman/5.7/en/set-transaction.html>`_
for detailed information.

.. _db-storage-engine-label:

MySQL / MariaDB storage engine
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Since ownCloud 7 only InnoDB is supported as a storage engine. There are some shared hosts who
do not support InnoDB and only MyISAM. Running ownCloud on such an environment is not supported.

Parameters
----------
For setting up ownCloud to use any database, use the instructions in :doc:`../../installation/installation_wizard`. You should not have to edit the respective values in the :file:`config/config.php`.  However, in special cases (for example, if you want to connect your ownCloud instance to a database created by a previous installation of ownCloud), some modification might be required.

Configuring a MySQL or MariaDB Database
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If you decide to use a MySQL or MariaDB database, ensure the following:

* That you have installed and enabled the ``pdo_mysql`` extension in PHP
* That the **mysql.default_socket** points to the correct socket (if the database runs on the same server as ownCloud).

.. note:: MariaDB is backwards compatible with MySQL.  All instructions work for both, so you will not need to replace or revise any, existing, MySQL client commands.

The PHP configuration in :file:`/etc/php5/conf.d/mysql.ini` could look like this:

::

  # configuration for PHP MySQL module
  extension=pdo_mysql.so

  [mysql]
  mysql.allow_local_infile=On
  mysql.allow_persistent=On
  mysql.cache_size=2000
  mysql.max_persistent=-1
  mysql.max_links=-1
  mysql.default_port=
  mysql.default_socket=/var/lib/mysql/mysql.sock  # Debian squeeze: /var/run/mysqld/mysqld.sock
  mysql.default_host=
  mysql.default_user=
  mysql.default_password=
  mysql.connect_timeout=60
  mysql.trace_mode=Off

Now you need to create a database user and the database itself by using the
MySQL command line interface. The database tables will be created by ownCloud
when you login for the first time.

To start the MySQL command line mode use::

  mysql -uroot -p

Then a **mysql>** or **MariaDB [root]>** prompt will appear. Now enter the following lines and confirm them with the enter key:

::

  CREATE DATABASE IF NOT EXISTS owncloud;
  GRANT ALL PRIVILEGES ON owncloud.* TO 'username'@'localhost' IDENTIFIED BY 'password';

You can quit the prompt by entering::

  quit

An ownCloud instance configured with MySQL would contain the hostname on which
the database is running, a valid username and password to access it, and the
name of the database. The :file:`config/config.php` as created by the
:doc:`../../installation/installation_wizard` would therefore contain entries like
this:

::

  <?php

    "dbtype"        => "mysql",
    "dbname"        => "owncloud",
    "dbuser"        => "username",
    "dbpassword"    => "password",
    "dbhost"        => "localhost",
    "dbtableprefix" => "oc_",

.. _db-postgresql-label:

Configure MySQL for 4-byte Unicode Support
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

For supporting such features as emoji, you have to enable 4-byte Unicode support in MySQL (instead of the default 3) *and* in ownCloud. 
If you have a new installation, you don’t need to do anything, as mb4 support is checked during setup, and used if available.
If it’s available, ownCloud is configured to use it. 

However, if you have an existing installation that you need to convert to use 4-byte Unicode support, then you need to do two things:

1. In your MySQL configuration, add the configuration settings below. If you already have them configured, update them to reflect the values specified:

:: 

  [mysqld]
  innodb_large_prefix=ON
  innodb_file_format=Barracuda
  innodb_file_per_table=ON

Then, run the following command:

::

  ./occ db:convert-mysql-charset

When this is done, tables will be created with a:

- ``utf8mb4`` character set.
- ``utf8mb4_bin`` collation.
- ``row_format`` of compressed.

For more information, please either refer to lines 1126 to 1156 in ``config/config.sample.php``, or have a read through the following links:

* https://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html#sysvar_innodb_large_prefix
* https://mariadb.com/kb/en/mariadb/xtradbinnodb-server-system-variables/#innodb_large_prefix
* http://www.tocker.ca/2013/10/31/benchmarking-innodb-page-compression-performance.html
* http://mechanics.flite.com/blog/2014/07/29/using-innodb-large-prefix-to-avoid-error-1071/
* http://dev.mysql.com/doc/refman/5.7/en/charset-unicode-utf8mb4.html

.. note:: 
   This is not required for new installations, only existing ones, as mb4 support is checked during setup, and used if available.

PostgreSQL Database
~~~~~~~~~~~~~~~~~~~

If you decide to use a PostgreSQL database make sure that you have installed
and enabled the PostgreSQL extension in PHP. The PHP configuration in :file:`/etc/php5/conf.d/pgsql.ini` could look like this:

::

  # configuration for PHP PostgreSQL module
  extension=pdo_pgsql.so
  extension=pgsql.so

  [PostgresSQL]
  pgsql.allow_persistent = On
  pgsql.auto_reset_persistent = Off
  pgsql.max_persistent = -1
  pgsql.max_links = -1
  pgsql.ignore_notice = 0
  pgsql.log_notice = 0

The default configuration for PostgreSQL (at least in Ubuntu 14.04) is to use the peer authentication method. Check :file:`/etc/postgresql/9.3/main/pg_hba.conf` to find out which authentication method is used in your setup.
To start the postgres command line mode use::

  sudo -u postgres psql -d template1

Then a **template1=#** prompt will appear. Now enter the following lines and confirm them with the enter key:

::

  CREATE USER username CREATEDB;
  CREATE DATABASE owncloud OWNER username;

You can quit the prompt by entering::

  \q

An ownCloud instance configured with PostgreSQL would contain the path to the socket on
which the database is running as the hostname, the system username the php process is using,
and an empty password to access it, and the name of the database. The :file:`config/config.php` as 
created by the :doc:`../../installation/installation_wizard` would therefore contain entries like
this:

::

  <?php

    "dbtype"        => "pgsql",
    "dbname"        => "owncloud",
    "dbuser"        => "username",
    "dbpassword"    => "",
    "dbhost"        => "/var/run/postgresql",
    "dbtableprefix" => "oc_",

.. note:: The host actually points to the socket that is used to connect to the database. Using localhost here will not work if PostgreSQL is configured to use peer authentication. Also note, that no password is specified, because this authentication method doesn't use a password.

If you use another authentication method (not peer), you'll need to use the following steps to get the database setup:
Now you need to create a database user and the database itself by using the
PostgreSQL command line interface. The database tables will be created by
ownCloud when you login for the first time.

To start the PostgreSQL command line mode use::

  psql -hlocalhost -Upostgres

Then a **postgres=#** prompt will appear. Now enter the following lines and confirm them with the enter key:

::

  CREATE USER username WITH PASSWORD 'password';
  CREATE DATABASE owncloud TEMPLATE template0 ENCODING 'UNICODE';
  ALTER DATABASE owncloud OWNER TO username;
  GRANT ALL PRIVILEGES ON DATABASE owncloud TO username;

You can quit the prompt by entering::

  \q

An ownCloud instance configured with PostgreSQL would contain the hostname on
which the database is running, a valid username and password to access it, and
the name of the database. The :file:`config/config.php` as created by the
:doc:`../../installation/installation_wizard` would therefore contain entries like
this:

::

  <?php

    "dbtype"        => "pgsql",
    "dbname"        => "owncloud",
    "dbuser"        => "username",
    "dbpassword"    => "password",
    "dbhost"        => "localhost",
    "dbtableprefix" => "oc_",

.. _db-troubleshooting-label:

Troubleshooting
---------------

How to workaround General error: 2006 MySQL server has gone away
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The database request takes too long and therefore the MySQL server times out. Its 
also possible that the server is dropping a packet that is too large. Please 
refer to the manual of your database for how to raise the configuration options 
``wait_timeout`` and/or ``max_allowed_packet``.

Some shared hosts are not allowing the access to these config options. For such
systems ownCloud is providing a ``dbdriveroptions`` configuration option within your
:file:`config/config.php` where you can pass such options to the database driver.
Please refer to :doc:`../../configuration/server/config_sample_php_parameters` for an example.

How can I find out if my MySQL/PostgreSQL server is reachable?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To check the server's network availability, use the ping command on
the server's host name (db.server.com in this example)::

  ping db.server.dom

::

  PING db.server.dom (ip-address) 56(84) bytes of data.
  64 bytes from your-server.local.lan (192.168.1.10): icmp_req=1 ttl=64 time=3.64 ms
  64 bytes from your-server.local.lan (192.168.1.10): icmp_req=2 ttl=64 time=0.055 ms
  64 bytes from your-server.local.lan (192.168.1.10): icmp_req=3 ttl=64 time=0.062 ms

For a more detailed check whether the access to the database server software
itself works correctly, see the next question.

How can I find out if a created user can access a database?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The easiest way to test if a database can be accessed is by starting the
command line interface:

**MySQL**:

Assuming the database server is installed on the same system you're running
the command from, use::

  mysql -uUSERNAME -p

To acess a MySQL installation on a different machine, add the -h option with
the respective host name::

  mysql -uUSERNAME -p -h HOSTNAME

::

  mysql> SHOW VARIABLES LIKE "version";
  +---------------+--------+
  | Variable_name | Value  |
  +---------------+--------+
  | version       | 5.1.67 |
  +---------------+--------+
  1 row in set (0.00 sec)
  mysql> quit

**PostgreSQL**:

Assuming the database server is installed on the same system you're running
the command from, use::

  psql -Uusername -downcloud

To acess a MySQL installation on a different machine, add the -h option with
the respective host name::

  psql -Uusername -downcloud -h HOSTNAME

::

  postgres=# SELECT version();
  PostgreSQL 8.4.12 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 4.1.3 20080704 (prerelease), 32-bit
  (1 row)
  postgres=# \q


Useful SQL commands
~~~~~~~~~~~~~~~~~~~

**Show Database Users**::

  MySQL     : SELECT User,Host FROM mysql.user;
  PostgreSQL: SELECT * FROM pg_user;

**Show available Databases**::

  MySQL     : SHOW DATABASES;
  PostgreSQL: \l

**Show ownCloud Tables in Database**::

  MySQL     : USE owncloud; SHOW TABLES;
  PostgreSQL: \c owncloud; \d

**Quit Database**::

  MySQL     : quit
  PostgreSQL: \q
   

