Basic Replication : Basic replication is implemented using standard CREATE SNAPSHOT or CREATE MATERIALIZED VIEW statements. It can only replicate data and not procedures, indexes replication is always one-way, and snapshot copies are read only.
Advanced Replication : Advanced replication supports various configurations of updatable snapshot, multi-master and update anywhere replication. It is more difficult to configure but allows data and other database objects like indexes and procedures to be replicated.
Differences between Basic and Advanced replications:
- With basic replication, data replicas provide read-only access to the table data whereas advanced replication features extend the capabilities of basic read-only replication by allowing applications to update table replicas throughout a replicated database system.
- With Basic Replication applications can query data from local data replicas. On the other hand with advanced replication, data replicas anywhere in the system can provide both read and update access to a table's data.
- Clustering means one than one database server configured for the same user connection. When users connect, one of the server’s responds and connects based on availability. The user is completely ignorant of the fact that there are more than one database servers. It demands high cost due to infrastructure needs. Clustering is hence done on server level.
- Mirroring means, one has many configured databases on the same server. Mirrors are basically copies of the original database. Mirroring is hence done on database level.
WATER MARK is a divided segment of used and free blocks. Blocks which are below high WATER MARK i.e. used blocks, have at least once contained some data. This data might have been deleted later. Oracle knows that blocks beyond high WATER MARK don’t have data; it only reads blocks up to the high WATER MARK during a full table scan.