Database mirroring allows for high availability and protection of SQL Server databases. It requires at least two SQL servers - a principal database and mirror database. A witness server is also used to automate failover between the principal and mirror databases. The document outlines the implementation steps, which include preparing the servers, backing up the principal database and transaction log, restoring the backup on the mirror server, and configuring security and mirroring settings between the principal, mirror and witness servers. Once setup is complete, the databases are mirrored and failover can occur automatically using the witness server.

1. Database Mirroring
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2. Preparation
• Minimum of two SQL servers
• Principal database/Mirror database
• “Witness” server (used for automatic
failover)
• Will be done using SQL Server 2005 SP2
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3. Types of mirroring
• High availability:
– Synchronized writes on principal and mirror
– Automated failover
– Requires witness server
• High Protection:
– Synchronized writes on principal and mirror
– Manual failover
– No witness server required
• High performance:
– Not synchronized (assumed writes will be completed on both
principal and mirror)
– Forced failover only
– Witness not required
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4. Implementation
• Will be using high availability method
• Requires at least three separate instances of SQL Server 2005 SP1
(Principal, Mirror, Witness)
• Ensure BlackBerry services on all machines are stopped
• Ensure the login credentials for all the SQL servers are the same
• Run the errors.sql script on all SQL servers before proceeding (the
errors.sql script can be found in the BES installation folder). You can
also get rid of the final line in the script (the USE database line) as it
may produce errors. -this is now an obsolete step. Running
errors.sql is no longer required for DB mirroring.
• It does not matter which servers you use for which purpose (i.e. M1
can be principal, M2 can be mirror and M3 can be witness for DB1
while M3 can be principal, M1 can be mirror and M2 can be witness
for DB2.)
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5. Implementation contd…
• Login to the SQL Server where your DB
exists
• Right-click->Properties->Options page
• Select “Full” option under recovery model
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7. Implementation contd…
• Backup the database
– Right-click->Tasks->Backup
– Ensure the backup type is “Full”
– On the options screen select “Overwrite all
existing backup sets” to ensure you are not
appending the backup set to an existing set
– Optionally you can also check “Verify backup
when finished” or “Perform checksum before
writing to media” for verification of data
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10. Implementation contd…
• Backup the transaction log
– Right-click->Tasks->Backup
– Ensure the backup type is “Transaction log”. When restoring on
the mirrored server, it may complain that no transaction log was
found and may fail the database restoration on the mirrored
server so this step is performed as a precaution
– On the options screen ensure that “Append to the existing
backup set” is checked. This will add the transaction log to your
previous full backup of the database so you only require to copy
the one .bak file to the mirrored server
– Optionally you can also check “Verify backup when finished” or
“Perform checksum before writing to media” for verification of
data
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13. Implementation contd…
• Copy the backups to another SQL Server
• Requires access to the SQL Server itself
(through remote desktop or VMware
console). What you want to do is copy the
backed up file you created in the previous
steps to the SQL server where you want
the database to be mirrored
• Where you place the backup files on the
second SQL Server does not matter
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14. Implementation contd…
• Restore the database on second SQL
Server
– Login to the SQL Server where your DB was
copied to
– Right-click on Database folder->Restore
backup
– Type the same name as the original database
on the first SQL Server in the “To database”
field
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16. Implementation contd…
• Select “From device” and click the “…”
button
• Click the add button and find the backup
file of the database
– Select the backed up database that you
copied from the principal SQL server
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18. Implementation contd…
• The two backups will appear in the
window
• Checkmark both backups
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20. Implementation contd…
• Select the options page
• At the bottom under “Recovery state”
select the second option (RESTORE
WITH NORECOVERY)
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22. Implementation contd…
• Your database should
now be listed in the
database folder on the
second SQL server and it
should be in the
“Restoring…” state
• *Note*: The “Restoring…”
state is indefinite for the
mirrored database. You
will not be able to access
a database while it is in
the restoring state.
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23. Setting up the mirroring
• Login to the first SQL Server:
– Select the Principal database
– Right-click->Properties
– Select the “Mirroring page”
– Click on “Configure security”
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26. Setting up the mirroring contd…
• On the Principal, Mirror and Witness
Server Instance screens, settings may be
grayed out due to the endpoint being
setup already for use. If this is the case
just select the appropriate server to
connect to and use the default settings. If
the endpoint has not been created yet,
you can create a new endpoint that will be
used for all database mirroring.
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28. Setting up the mirroring contd…
• If creating a new endpoint, use the default
port of 5022 and enter any name for the
endpoint. Use the same name on the
following servers for consistency although
using different names does not affect the
mirroring in any way.
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29. Setting up the mirroring contd…
• When selecting the Mirror and Witness
Server Instances, you may be required to
connect to these servers using some form
of authentication before you are able to
continue. For consistency use the same
logins for all servers.
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31. Setting up the mirroring contd…
• The next screen you may encounter will
ask for service accounts. This screen is to
grant CONNECT permissions for the
accounts that are running the SQL
services on each machine. Generally all
the SQL Server should be run on the
same account so you can just leave the
fields blank.
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33. • Click finish and
the database
mirroring should
be setup
successfully.
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35. Setting up the mirroring contd…
• Ensure the settings are correct in the
Mirroring window
• Synchronous operating mode should be
selected
• Click on start mirroring
• Status should show the database is now
mirrored correctly
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36. Setting up the mirroring contd…
• Your databases
should now be in the
following states
• Upon failover, the
mirror database will
become principal and
the principal database
will become the mirror
(similar in function to a
high availability BES
with the
active/standby states)
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