What is Replication and Database Mirroring?

Thanks for the invitation and I'm sorry because sql is not my expertise.

Database mirroring involves two copies of a single database that typically reside on different computers. At any given time, only one copy of the database is currently available to clients.

Replication failover to a mirror is fully supported for publication databases, with limited support for subscription databases. Database mirroring is not supported for the distribution database.

 

These are two high data availability techniques for database servers.

Replication is the process of copying and distribution of a database and database object from one  into another database. it reduces the load from original database server, and all the server on which the database is copied are as active as master server.

 

Database mirroring creates two copies of database in different  server instances.  the mirror copy database will only work as stand by copies and are always not active like in the case of replication. Database Mirroring is limited to only two servers.

 

Replication is to make a clone copy of your records to a secondary database via a synchronisation process. 

Database mirroring although it sound similar, is actually cloning the database to a secondary server.

The stark difference between the two is that replication works on the record level whilst mirroring works on the database level. That means to say, replication only apply data changes and does not apply any table structure change to the secondary database. 

I have seen this happening on site, where the replication failed at some point because someone changed the table structure of the primary database that wasn't applied to the secondary database. As a result the whole replication failed. 

Contrary to the above, database mirroring handles both the table structure and data change as it apply the delta change of the whole database. 

Hope this helps.

Check this article , I think it will help you HERE

Replication VS Mirroring, and what to use for a Disaster Recovery setup One question I seem to get asked a lot is what is the difference between Replication and Mirroring when it comes to SQL, and especially for the Sys Admin stuck in the middle, what is the best one to use for a Disaster Recovery scenario.Firstly, for people who haven't heard of either, both replication and mirroring are methods of transferring data from a primary database, to a secondary database or databases. Two common scenarios for this are to have a separate copy of the database for reporting purposes, or to have a copy of the database safely off site in the event of disaster on the primary database. In theory both Replication and Mirroring have the same purpose, to shift data from your database to other locations, but each method has a very different application and way of going about things. Obviously nothing in these guides are black and white, completely right or wrong, but as a general rule this is the way you would apply these methods.Replication - Reporting and database synchronization

• Secondary database is online and searchable. Basically you can run queries against your secondary database and treat it like a normal database while protecting the performance of your primary database.
• There are different forms of replication
  • Transactional - Reads transactions to your secondary DB(s) as they occur on your Primary with a slight delay
  • Snapshot - Takes dumps at scheduled times of the changes recorded in your logs since the last synch, and inserts them at a scheduled time
  • Merge - This does what it says on the tin. It will merge content between databases so you can update data in both DB's. You might use this if you have two identical databases from day 1, and you have App 1 talking to DB 1, and App 2 talking to DB 2 for load balancing purposes or something. At the end of the day you might want to merge the transactions that occurred during the day to make sure you have two full lists of transactions in each DB.

Mirroring - Disaster Recovery 

• Secondary database is in an offline mode while mirroring is in place. This is to ensure integrity in the secondary database in the event of a failover being required. Nothing can write to the secondary database, so you know it will exactly match your primary.
• Can replicate schema changes. What this means is if you add a new index, or a new table, it will automatically be mirrored over. This is not the case with replication, it will only transfer across data level changes.

There are many configurations you can put together for replication, or mirroring, and you'd have to identify exactly what setup would suit your needs, but the above is a good baseline as to the best practices. 

Replication is a set of technologies for copying and distributing data and database objects from one database to another and then synchronizing between databases to maintain consistency.

Database mirroring is a solution for increasing the availability of a SQL Server database. Mirroring is implemented on a per-database basis and works only with databases that use the full recovery model.  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 adatabase mirroring session, between these server instances.

a copy of your database store in another location. so that in future your primary hard disk failure accidently, secondary disk will save you!

Everytime a comand is executed, the replicated database will also affected by updating itself.

This feature will be removed in a future version of Microsoft SQL Server. Avoid using this feature in new development work, and plan to modify applications that currently use this feature. Use Always On Availability Groups instead.

Replication is copying something from one location & pasting it on other through an automated process or called Stored Procedure.

Replication :Secondary database is online and searchable. Basically you can run queries against your secondary database and treat it like a normal database while protecting the performance of your primary database

Mirroring:Secondary database is in an offline mode while mirroring is in place. This is to ensure integrity in the secondary database in the event of a failover being required. Nothing can write to the secondary database, so you know it will exactly match your primary