Pre-Commit Handlers

A pre-commit handler is a PL/SQL procedure that takes the commit SCN from an internal commit directive in the queue used by the Apply process. The pre-commit handler may use and process the commit information in any suitable way. For example, an auditing process can be developed using the commit information.

Logical Change Record Events

LCRs represent the redo changes that are converted into events. A Capture process reformats changes that are captured from the redo log into LCRs. The LCR is an object with a specific format that describes a database change.

The Capture process converts the database changes into events containing LCRs and subsequently enqueues them into a queue. A Capture process is always associated with a single SYS.AnyData queue and it only enqueues events into this queue.  For improved performance, captured events are always stored in a buffered queue, which is SGA memory associated with a SYS.AnyData queue. Multiple queues can be created and a different Capture process can be associated with each queue.

A Capture process creates two types of LCRs: Row LCRs and DDL LCRs.