Online Versus Offline Backups •In addition to databases, the backup can include any related files such as log or configuration files. •Data from  MEMORY  tables is tricky to back up this way because their contents are not stored on disk. (The MySQL Enterprise Backup product has a feature where you can retrieve data from  MEMORY  tables during a backup.) •Backups are portable only to other machines that have identical or similar hardware characteristics. •Backups can be performed while the MySQL server is not running. If the server is running, it is necessary to perform appropriate locking so that the server does not change database contents during the backup. MySQL Enterprise Backup does this locking automatically for tables that require it. •Physical backup tools include the  mysqlbackup  of MySQL Enterprise Backup for  InnoDB  or any other tables, or file system-level commands (such as  cp ,  scp ,  tar ,  rsync ) for  MyISAM  tables. •For restore: •MySQL Enterprise Backup restores  InnoDB  and other tables that it backed up. • ndb_restore  restores  NDB  tables. •Files copied at the file system level can be copied back to their original locations with file system commands. Logical backup methods have these characteristics: •The backup is done by querying the MySQL server to obtain database structure and content information. •Backup is slower than physical methods because the server must access database information and convert it to logical format. If the output is written on the client side, the server must also send it to the backup program. •Output is larger than for physical backup, particularly when saved in text format. •Backup and restore granularity is available at the server level (all databases), database level (all tables in a particular database), or table level. This is true regardless of storage engine. •The backup does not include log or configuration files, or other database-related files that are not part of databases. •Backups stored in logical format are machine independent and highly portable. •Logical backups are performed with the MySQL server running. The server is not taken offline. •Logical backup tools include the  mysqldump  program and the  SELECT ... INTO OUTFILE statement. These work for any storage engine, even  MEMORY . •To restore logical backups, SQL-format dump files can be processed using the  mysql  client. To load delimited-text files, use the  LOAD DATA  statement or the  mysqlimport  client. Online Versus Offline Backups Online backups take place while the MySQL server is running so that the database information can be obtained from the server. Offline backups take place while the server is stopped. This distinction can also be described as “hot”  versus “cold”  backups; a “warm”  backup is one where the server remains running but locked against modifying data while you access database files externally. Online backup methods have these characteristics: 1613