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
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.