Summary

MarkLogic Server has several different features that can help manage data across multiple database instances. Those features differ from each other in several important ways - this article will focus on high-level distinctions and will provide pointers to other materials to help you decide which of these features could work best for your particular use case.

 Details

Backup/Restore - database backup and restore operations in MarkLogic Server provide consistent database-level views of your data. Propagating data from one instance to another via backup/restore involves a MarkLogic administrator using a completed backup from the source instance as the restore archive on the destination instance. You can read more about Backup/Restore here: http://docs.marklogic.com/guide/admin/backup_restore.

Flexible Replication - can be used to maintains copies of data on multiple MarkLogic Servers. Unlike backup/restore (which relies on taking a consistent, database level view of the data at a particular timestamp), Flexible Replication creates a copy of a document in another database and keeps that copy in sync (possibly with some time-lag/latency) with the original in the course of normal operations. You can read more about Flexible Replication here: http://docs.marklogic.com/guide/flexrep/rep_intro. Do note that:

• Flexible Replication is asynchronous. Asynchronous Replication refers to a configuration in which the Master does not wait for confirmation that the update has been received by the Replica before sending further updates.
• Flexible Replication does not use the same transaction boundaries on the replica as on the master. For example, 10 documents might be inserted in a single transaction on a Flexible Replication master. Those 10 documents will eventually be inserted on a Flexible Replication replica, but there is no guarantee that the replica instance will also use a single transaction to do so.

Database Replication - is used maintains copies of data on multiple MarkLogic Servers. Database Replication creates a copy of a document in another database and keeps that copy in sync (possibly with some time-lag/latency) with the original in the course of normal operations. You can read more about Database Replication here: http://docs.marklogic.com/guide/database-replication/dbrep_intro. Note that:

a. Database Replication is, like Flexible Replication, asynchronous.

b. In contrast to Fleixble Replication, Database Replication operates by copying journal frames from the Master database and replays the transactions described by those journal frames on the foreign Replica database.

XA Transactions - MarkLogic Server can participate in distributed transactions by acting as a Resource Manager in an XA/JTA transaction. If there are multiple MarkLogic Server instances participating as XA resources in a given XA transaction, then it's possible to use that XA transaction as a synchronized means of replicating data across those multiple MarkLogic instances. You can read more about XA Transactions in MarkLogic Server here: http://docs.marklogic.com/guide/xcc/concepts#id_57048.