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Not much information on this.
The ApplyParallel configurable database property specifies whether Redo Apply should use multiple processes to apply redo data to the physical standby database.
Source - Oracle® Data Guard Broker 11g Release 2 (11.2) Part Number E17023-08
So the way I read it, it just multiple processes
Kind of a vague note here too :
Tiny bit more here :
Emre Baransel site
Edited by: mseberg on Mar 27, 2013 1:51 PM
Edited by: mseberg on Mar 27, 2013 2:37 PM
I believe it's the same concept of Parallel Recovery
Not using Parallel Recovery
This single process will read the archived logs and determine which changes are required for the specific data files being recovered. The data block is read into the buffer cache, and the
redo is applied to it. Each time an archived log is completely applied, a media recovery checkpoint occurs which signals DBWR to write all the dirty blocks in the buffer cache to the data files.
Using Parallel Recovery
The process that issues the recovery command reads the archived logs as before, but instead of reading the blocks in the cache and applying the redo to them directly, it passes that work to the parallel execution slave processes. To make sure the redo is applied to the data files in SCN order, the parallel slaves work on different ranges of data blocks, so
they will not interfere with each other, and also the redo will still get applied in SCN order for each data block.