Microsoft sql server 2000 mirroring

Unlike the two failover partners, the witness does not serve the database. Supporting automatic failover is the only role of the witness.

Database mirroring maintains two copies of a single database that must reside on different server instances of SQL Server Database Engine. Typically, these server instances reside on computers in different locations. Starting database mirroring on a database, initiates a relationship, known as a database mirroring session , between these server instances.

One server instance serves the database to clients the principal server. The other instance acts as a hot or warm standby server the mirror server , depending on the configuration and state of the mirroring session. When a database mirroring session is synchronized, database mirroring provides a hot standby server that supports rapid failover without a loss of data from committed transactions.

When the session is not synchronized, the mirror server is typically available as a warm standby server with possible data loss. The principal and mirror servers communicate and cooperate as partners in a database mirroring session. The two partners perform complementary roles in the session: the principal role and the mirror role.

At any given time, one partner performs the principal role, and the other partner performs the mirror role. Each partner is described as owning its current role. The partner that owns the principal role is known as the principal server , and its copy of the database is the current principal database. The partner that owns the mirror role is known as the mirror server , and its copy of the database is the current mirror database.

When database mirroring is deployed in a production environment, the principal database is the production database. Database mirroring involves redoing every insert, update, and delete operation that occurs on the principal database onto the mirror database as quickly as possible.

Redoing is accomplished by sending a stream of active transaction log records to the mirror server, which applies log records to the mirror database, in sequence, as quickly as possible. Unlike replication, which works at the logical level, database mirroring works at the level of the physical log record. Beginning in SQL Server , the principal server compresses the stream of transaction log records before sending it to the mirror server.

This log compression occurs in all mirroring sessions. A given server instance can participate in multiple concurrent database mirroring sessions with the same or different partners.

A server instance can be a partner in some sessions and a witness in other sessions. 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. Under synchronous operation, a transaction is committed on both partners, but at the cost of increased transaction latency. There are two mirroring operating modes. One of them, high-safety mode supports synchronous operation.

Under high-safety mode, when a session starts, the mirror server synchronizes the mirror database together with the principal database as quickly as possible. As soon as the databases are synchronized, a transaction is committed on both partners, at the cost of increased transaction latency.

The second operating mode, high-performance mode , runs asynchronously. The mirror server tries to keep up with the log records sent by the principal server. The mirror database might lag somewhat behind the principal database. However, typically, the gap between the databases is small. However, the gap can become significant if the principal server is under a heavy work load or the system of the mirror server is overloaded.

I select full backup when backup it, do you mean the full backup don't contain the log? I has tried to copy the log backup, and the log backup is "trn" file, but it can't be copied to the backup server.

You should back Up a Transaction Log like this What error did you get when you couldn't copy? Thanks, Yufeishao-msft for your contribution and providing the information. Skip to main content. Search icon An illustration of a magnifying glass.

User icon An illustration of a person's head and chest. Sign up Log in. Web icon An illustration of a computer application window Wayback Machine Texts icon An illustration of an open book. Books Video icon An illustration of two cells of a film strip. You have three options. Improve this answer. NotMe NotMe Think I will go with an upgrade — PeteT.

Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Stack Gives Back