SQL Server Replication
High Availability: In today’s business needs server availability
has to be 99.99% with requires very less down time .High availability (HA) is
one of the essential features which will help business achieve maximum
availability of enterprise RDBMS.
Replication, Alwaysongroups , Clustering and Database mirroring
are some of the High Availability technologies. In this post we will discuss
about replication. Replication means copying. Three parts of replication are
publisher, distributor and receiver. Replication can be uni direction that
means data flows from in one direction Publisher to subscriber through
distributor and can be bi directional i.e it can flow from subscriber to
publisher also. Tables are referred as articles and tables with primary keys
are eligible for replication.
Publisher: Is the database on which we want to track things. Any
transactions happen on Publisher need to be tracked and moved to subscriber.
Subscriber: Is the receiver database. This is the database on
which we want things to be copied. This
database is also called secondary database. There can be more than one subscriber
for a publication.
Distributor: It acts like a post man. It tracks the transactions
happening on the Publisher database and sends the files to be executed on
subscriber and sees that both the publisher and subscriber are always synced.
Distributor can be on a separate server or it can be either on publisher or
subscriber.
Types of replication:
1. Transnational Replication
2. Merge Replication
3. Snapshot Replication
4. peer to peer Replication
Replication agents: replication agents are stand alone programs/
jobs created as a part of replication to facilitate the replication process. Replication
agents are created as jobs under SQL server agent. The following are the common
Replication agents.
1. Replication log reader
agent
2. Replication
Distribution agent
3. Replication Snapshot
agent
4. Replication Merge agent
5. Replication Queue
Reader agent
6. Replication Agent
administration
More Info about Replication
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