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What do you need to know about Database mirroring?
For an introduction to database mirroring, see Database Mirroring (SQL Server). This section introduces a few terms that are central to this topic. The database mirroring session operates asynchronously and uses only the principal server and mirror server. The only form of role switching is forced service (with possible data loss).
What happens to replication when database is no longer mirrored?
If the publication database at the principal is no longer mirrored, replication continues to work unchanged against the original principal. If the publication database fails over from the principal to the mirror and the mirroring relationship is subsequently disabled or removed,…
Which is the database mirroring operating mode in SQL Server?
For information about editions that fully support database mirroring, see “High Availability (Always On)” in Editions and Supported Features for SQL Server 2016. When transaction safety is set to OFF, the database mirroring session operates asynchronously. Asynchronous operation supports only one operating mode-high-performance mode.
What does asynchronous operation do in a mirror server?
Transactions commit without waiting for the mirror server to write the log to disk. Asynchronous operation permits the principal server to run with minimum transaction latency. The mirror server attempts to keep up with the log records sent by the principal server.
mirror server. In a database mirroring configuration, the server instance on which the mirror database resides. principal database. In database mirroring, a read-write database whose transaction log records are applied to a read-only copy of the database (a mirror database).
What are two common configurations for SQL Server mirroring?
One of the common mirroring configuration is the environment with two SQL Servers (SQLServer-1 and SQLServer-2), two instances (SQLInstance-1 and SQLInstance-2), and one mirrored database named SQLDB-1. The second common configuration is the environment with one SQL Server machine, two SQL Server instances, and one mirrored database named SQLDB-1.
When does a database mirroring session become synchronized?
At the start of a database mirroring session, the mirror and principal databases are in this state. Icon: Standard database cylinder, status Synchronized. When the mirror server becomes sufficiently caught up to the principal server, the database state changes to Synchronized.
What is the status of a mirror server?
The principal server instance is sending log records to the mirror server instance, which is applying the changes to the mirror database to roll it forward. At the start of a database mirroring session, the mirror and principal databases are in this state. Icon: Standard database cylinder, status Synchronized.
Who is the principal server in database mirroring?
In database mirroring, the partner whose database is currently the principal database. Received transaction log records that are waiting on the disk of a mirror server. The principal server and mirror server perform complementary principal and mirror roles. Optionally, the role of witness is performed by a third server instance.
Do you have to run the same SQL Server as the mirror server?
The mirror server instance must be running the same edition of SQL Server. A database mirroring session runs with either synchronous or asynchronous operation. Under asynchronous operation, the transactions commit without waiting for the mirror server to write the log to disk, which maximizes performance.
How does role switching work in database mirroring?
Within the context of a database mirroring session, the principal and mirror roles are typically interchangeable in a process known as role switching. Role switching involves transferring the principal role to the mirror server.