Logical Standby Database in Oracle

Logical Standby Database in Oracle

What is a logical standby database?

  • Apart from Physical and Snapshot Standby Database, it is another type of Standby Database.
  • It is an active database that can be read-write in open mode.
  • Reporting and querying can be done. Thus, it can reduce the load of the production database with correct usage.
  • Since the Logical Standby is not a Block by block standby database, the Logical Standby does not pass any physical corruption on the Primary database to the Logical Standby.
  • Logical standby has the ability to make Switchover and Failover.
  • Its most important feature is that it can be used in Oracle Database Software and Patch upgrades.
  • Redos in Physical Standby were replicated as Redo-Apply. In Logical Standby, it is replicated as SQL Apply. It performs this with LogMiner Technology.

Reader: Reads redo records from Redo Buffer Cache or Archive redo log files.

Preparer: Converts block level changes to Logical Change Records. The concept of transaction does not yet exist.

Builder: Creates transactions from single LCRs. The concept of transaction now exists.

Analyzer: Groups transactions by analyzing whether there is a dependency between different transactions.

Coordinator: Gives the Logical Standby the commitment to make changes.

Applier: Processes LCRs into database.

  • SQL Apply is done by LSP process.

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