You work as the database administrator at Domain.com. The Domain.com network consists of a single Active Directory domain named Domain.com. All servers on the Domain.com network run Windows Server2003. The Domain.com network contains three SQL Server 2005 database servers named Certkiller -DB01, Certkiller -DB02, and Certkiller -DB03. Database mirroring is configured between Certkiller -DB01 and Certkiller -DB02, with Certkiller -DB03 as the witness server. Certkiller -DB01 is the principal database server and hosts a database named CK_Sales that stores sales data from Domain.com’s e-Commerce Web site.
The size of the CK_Sales database has increased over the last three month as Domain.com’s customer base has increased. You are concerned about the performance of the CK_Sales database. You want to maximize database performance while retaining the mirrored configuration.
What should you do?

A.
Configure the database mirroring session to run in synchronous operation.

B.
Configure the database mirroring session to run in asynchronous operation.

C.
Configure the database mirror to operate in high-safety mode.

D.
Configure the database mirror to operate in high-availability mode.

Explanation:
Asynchronous mode provides the best performance fro mirrored databases at the expense of data recovery. During asynchronous mode, a transaction is committed to the principal database without requiring the principal database to wait for the mirror database to write the transaction log to disk. This means that the principal database can operate with minimum transaction lag.
Incorrect Answers:
A, C: High-safety mode supports synchronous operation. Transaction latency occurs in this mode as a transaction must be committed to both partners. In Asynchronous mode a transaction is committed to the principal database without requiring the principal database to wait for the mirror database to write the transaction log to disk. This maximizes performance for the mirrored database.
D: SQL Server 2005 does not have a high-availability mode for database mirroring. It only has high-safety mode, which supports synchronous operation; and high-performance mode, which supports asynchronous operation.
Reference:
Microsoft SQL Server 2005 Books Online (2006), Index: database mirroring [SQL Server], about database mirroring
Microsoft SQL Server 2005 Books Online (2006), Index: database mirroring [SQL Server], asynchronous
Microsoft SQL Server 2005 Books Online (2006), Index: database mirroring [SQL Server], synchronous