An SQL dump of a database is a common method to safely store away a snapshot of the database for archival purposes or to migrate data between database instances, e.g. between two major system releases. The content of a SQL dump is a large collection of SQL commands in ASCII. Running the script will recreate the database in the same state as it was when the dump was created. Since MonetDB does not provide global locking schemes, a time-consuming dump operation may become invalidated by a concurrent update query.
The primary tool to consider for making an ASCII dump is msqldump, which includes a wide variety of options. A simplified version is available as part of the mclient program.
Consider you have already installed the SQL tutorial database voc and wish to transport it to another machine. Then the following client command line option generates the dump file.
shell> mclient -lsql --database=voc --dump >/tmp/voc.sql
You can inspect the file /tmp/voc.sql to confirm that indeed a readable database dump is available. If storage space is a problem, you can readily pipe the output of this command to a compression tool or sent it directly to another machine in your environment using conventional Linux tools. As a baseline, move the file over to the new machine. The monetdb tool can be used to create the database on that machine. Once done, it suffices to feed the dump file to mclient to populate the database.
Creation of the dump respects your credentials, which means you only can dump the tables you have access to.
shell> mclient -lsql --database=voc /tmp/voc.sql
Migration of a database from other system follows the same route, but be aware that SQL dialects often differ. A manual or scripted patch of a foreign SQL dump is often needed.
Fast backups on Linux
Aside from the ASCII dumps, one can also take the database server out of production using the following commands. Be careful in using shutdown(), because there may be users running transactions. This can be seen using the sys.sessions table.
shell> mclient -d demo
select * from sys.sessions;
shell> monetdb stop demo
shell> monetdb lock demo
After the database has been securely stopped, we can create a copy of the database directory in the dbfarm and put it aside in a safe place. Alternatively, incremental file-system dumps can be used to reduce the time and storage space for a recovery point. Finally, the database is released for production again
shell> monetdb release demo
It is recommended to always dump the old database into ASCII before installing a new MonetDB release. Subsequently remove the dbfarm. After installation, the dump can be restored.
To dump the SQL database, start the MonetDB SQL Client program and type the command
The path after \> should be an absolute path name (i.e. start with a drive letter) and be in a save location. By default the database is located in
%APPDATA%\MonetDB5. After having made a database dump it can be removed. This folder is located inside the dbfarm\demofolder.
Restoring the SQL database can be done using the MonetDB SQL Client program with the following command