Backing Up the Database
vBulletin makes this job quite easy as long as your database isn't too big. How big is too big depends on a variety of factors, but if your database is under 250 Mb, you should be able to use this feature just fine.
Back to basics
For large databases, saving the database via the command line is recommended. This is done using the following command:
shell> mysqldump --tab=/path/to/some/dir --opt db_name
The backup interface is easy to use. It shows you all the tables that are available in the database that contains vBulletin (including non-vBulletin tables).
You should choose the tables you want to back up (it's probably best to choose all the tables initially) and then select at the bottom of the screen the location to save the backup to. This has to be a folder on the server that vBulletin can write to, so its chmod permission should be set to 777.

After you have done this, click on Save. The backup will then be carried out.
You can also back up single database tables into a CSV (comma separated variable) file, which is handy if you plan on making changes to the database.

Restoration of this database is carried out through the phpMyAdmin interface.
Command-line recovery
Recovery of a database through the command line is a two-step process. First, create a database to receive the data.
$ mysql -h localhost -u XXXXXX -p YYYYYY
Here XXXXXX is the username of the database and YYYYYY is the password.
Then move the data to the new database:
$ mysql -h localhost -u XXXXXX -p YYYYYY restored < db_name
Repairing and Optimizing the Database
Again, this process gives you access to all the tables in the database, not just the tables relating to vBulletin. You can choose to repair and optimize some of the tables, or you can repair and optimize all the tables.
At the bottom of the page choose whether you want to optimize the tables, repair the tables, or carry out both operations.

Backup first!
Make sure that you have an up-to-date backup before carrying out the repair/optimize process.

It is recommended that you run the repair/optimize process twice to make sure all problems are fixed.
Some Maintenance Issues
The Update Counterspage enables you to change many of the counters in the database.
Take your time
This process can take a lot of time there is no way to rush it, so it's best to start it and leave it to finish on its own.
These counters are important for the smooth running of the database, but they may require updating following a change to the database. These are some of the changes that you may need to make:
• Updatetheforums This feature will update the information for each forum including last post information, thread count, and post count. This operation can be carried out after a mass moving or pruning of threads and posts.

• Update user titles This will go through every user on the forums and determine their correct user title.
• Update user names This will update user names everywhere they occur on your forums. This operation may need to be done after changing a user's name in the AdminCP.
• Update post counts This will update the post count for each user by counting how many posts they have in the database. If someone has artificially inflated or deflated post counts by editing profiles in the AdminCP, then this procedure will reset the post counts to their true values.
• Fix broken user profiles This will fix any broken user profiles.
• Rebuild forum information This will update the forum counters (post counts) and also check for orphan moderators. You may need to do this after merging or deleting threads or posts in your forums.
• Rebuild thread information This will update the thread counters including last post information, reply count, and view count. You may need to do this after moving or pruning threads or posts.
• Rebuild similar threads This will search the forums for threads that are similar to each other. To show similar threads you need to enable the option in the vBulletin options. If you want your forums to search for similar threads when a new thread is posted (rather than having to update this counter later), then you need to enable the option on this page.
• Rebuild search index This will need to be done after changing the max/min search word length in the vBulletin options.
• Rebuild statistics This will rebuild the information that is displayed on the vBulletin Statistics page.
• Rebuild post cache vBulletin doesn't parse vB code in posts each time they are displayed. Instead the parsed posts are saved in the post_parsed table. This reduces the processing time needed to display a post. Updating this counter will rebuild the parsed posts. This needs to be done after changing vB codes or posting allowances.
• Delete duplicate threads

• Delete duplicate threads Sometimes duplicate threads are created during the posting process. Updating this counter will remove those duplicates.
• Rebuild styles Updating this counter will rebuild the style structure.
• Rebuild attachment thumbnails Rebuilding thumbnails is necessary after changing the thumbnail settings in the vBulletin options.

• Rebuilduserreputation You will need to update this counter if you change the default reputation value in the vBulletin options.
• Removeorphanthreads This will delete any threads that belong to forums that no longer exist.
• Removeorphanposts This will delete any posts that belong to threads that no longer exist.