How to Increase database / log size of mirrored database

Question

Hi All,
I have been asked to increase the default database and log size of two databases, both of which are mirrored.
I have been trying to find out what else I need to do in this case other than the standard resizing.
Are there extra steps I need to perform as these dbs are mirrored (SQL Mirroring)?
Farren

Answer 1

Hi Farren,
Based on my test, if you choose to expand the mirrored database by increasing the size of an existing data or log file, you can directly execute the ALTER DATABASE statement on the Principal server as Uri’s post, but before that please make sure the mirroring
status is synchronized. You can check the mirroring configuration and partner status with the following query.
SELECT DB_NAME(DATABASE_ID) 'DBNAME',mirroring_state,
mirroring_state_desc,mirroring_role,mirroring_role_desc,
mirroring_partner_name,mirroring_partner_instance
FROM sys.database_mirroring
WHERE mirroring_guid IS NOT NULL
However, if you choose to expand the mirrored database by adding a new file to the database, you need to perform extra steps as follows.
   1. Check the mirroring configuration and partner status with above query.
   2. Run the below command on the principal server to break the mirror.  
ALTER DATABASE DatabaseName SET PARTNER OFF
   3. Create your database file on the principal server.
   4. Run a log backup on the principal server.
   5. Restore this log backup on the mirrored server using the NORECOVERY and MOVE options.
   6. Re-establish mirroring between the servers for this database.
Reference:
Increase the Size of a Database
How to add a database file to a mirrored SQL Server database
Thanks,
Lydia Zhang
Lydia Zhang
TechNet Community Support