1. System Databases Recovery
The master database contains key database
and security information, and the msdb
database holds the schedules and jobs for SQL Server, as well as the
backup history. A complete recovery plan must include the system
databases.
Master Database
The master database, by default, uses
the simple recovery model. Using only full backups for the master
database is OK; it's not a transactional database.
Backing Up the Master Database
You back up the master database in the same manner as user databases.
Be sure to back up the master database when doing any of the following:
- Creating or deleting databases
- Modifying security by adding logins or changing roles
- Modifying any server or database-configuration options
Because the msdb database holds a record of all backups, back up the master database and then the msdb database.
Recovering the Master Database
If the master database is corrupted or
damaged, SQL Server won't start. Attempting to start SQL Server will
have no effect. Attempting to connect to the instance with Management
Studio invokes a warning that the server does not exist or that access
is denied. The only solution is to first rebuild the master database
using the command line setup as shown next, reapply any SQL Server
updates, start SQL Server in single-user mode, and restore the master
database.
1. Rebuild the master database using the command line setup:
setup /QUIET /ACTION=REBUILDDATABASE /INSTANCENAME="<instance name>"
/SQLSYSADMINACCOUNTS="<DomainName\UserName >" /SAPWD="<password>"
where
- setup.exe is either from your
original installation media or the “local” setup.exe as found in the
110\Setup Bootstrap\SQLServer2012 directory.
- /QUIET switch suppresses all error messages.
- /ACTION=REBUILDDATABASE switch rebuilds all the system databases.
- /INSTANCENAME switch specifies the name of your SQL Server named instance. Use MSSQLServer for “<instance_name>” for default instance.
- /SQLSYSADMINACCOUNTS switch
corresponds to the currently-logged in domain user running this rebuild
process. The user must be a member of the SQL instance's sysadmin
server role.
- /SAPWD switch is used to indicate a new SA password if you configured SQL Server for mixed authentication.
Note
A new feature was added to rebuilding
the system databases in the last release. The system databases used for
rebuilding the local system databases no longer come from the original
installation media and are located locally in the C:\Program Files\Microsoft SQL Server\MSSQL11.MSSQLSERVER\MSSQL\Binn\Templates\C:\Program
Files\Microsoft SQL Server\110\Setup
Bootstrap\SQLServer2012SQLServer2012 folder. The switches have changed
as compared to SQL Server 2005. folder, and setup.exe is located in the
2. Run the following from the command prompt to start a default instance of SQL Server in single user mode:
sqlservr.exe -m
If the instance is a named instance of SQL Server in single user mode, run the following to start:
sqlservr.exe -m -s <instancename>
3. Reapply any SQL Server updates, service packs, and hotfixes previously applied to the SQL Server.
4. Restore the
master database as you would a user database. If a master backup is not
available, re-create all missing entries for your user databases,
logins, endpoints, and so forth.
If the master database is accessible, start SQL
Server in single-user mode, and then restore the master database as you
would a user database.
Note
Rebuilding the master database also
rebuilds the msdb and model databases. After rebuilding the databases,
restore the system databases (master, msdb, and model) from the most
recent good backup.
Rebuilding the master database
installs all system databases to their initial location. If initially
one or more system databases were moved to a different location, a
similar move is required again.
MSDB System Database
Like the master database, the msdb database, by default, uses the simple recovery model.
Because the msdb database contains information
regarding the SQL Server Agent jobs and schedules, as well as the
backup history, it should be backed up whenever you do the following:
- Perform backups.
- Save SSIS packages.
- Create new SQL Server Agent jobs.
- Configure SQL Server Agent mail or operators.
- Configure replication.
- Schedule tasks.
- Create or modify any policies created in Policy-Based Management.
- Configure or modify Management Data Warehouse.
- Add new registered servers (if an instance is set up as Central Management Server).
The msdb database is backed up in the same way that a user database is backed up.
To restore the msdb database, you do not need to
put the server in single-user mode as you do with the master database.
However, it's still not a normal restore because without a current
msdb, Management Studio is not aware of the backup history. Therefore,
the msdb backup can't be chosen as a backup database but must be
selected as a backup device.
Use the Contents button to check the disk device
for specific backups. If several backup instances are in the backup
device, you can use the Contents dialog box to select the correct
backup. It then fills in the file number in the restore form.
Note
Before restoring the msdb
database, stop SQL Server Agent. This is to ensure that the msdb
database is not accessed by the SQL Server Agent and allows the restore
to complete.
2. Performing a Complete Recovery
If the server has completely failed and all the backups must be restored onto a new server, follow these steps:
1. Build the Windows server, and restore the domain logins to support Windows authentication.
2. Install SQL Server and any service-pack, cumulative updates, security upgrades, or hotfixes.
3. Start SQL Server in single-user mode, and restore the master database.
4. Verify that SQL Server Agent is stopped. Restore the msdb database.
5. If the model database was modified, restore it.
6. Restore the user databases.
Best Practice
Performing a flawless recovery is a
“bet your career” skill. Take the time to work through a complete
recovery of the production data to a backup server. The confidence you
gain can serve you well as a SQL Server DBA.
