12.1.0.2
Precursor to save you and me time.
If theres a chance youre going to reply with "thats not oracles problem", stop reading.
If theres a chance youre going to ask "what are you going to DIFFERENT when YOU find out" Stop reading,
Other than that, here we go
I need to have a certain amount of control over the amount of REDO that I generate at certain times of the day. I have a third party tool that can only read logs at a particular speed and I need changes to propagate elsewhere in a timely manner. Excessive REDO slows this up.
Ive been monitoring the amount of REDO that individual sessions generate, I can move unnecessary jobs. All good to here.
Im seeing mulltiple gigabytes being generated during busy periods by the space management process Wnnn. For example this morning I had about 50gb of REDO in total over an hour of which 15gb of that was from the Wnnn processes.
Now we can find out what this does by looking at the docs.
"
Wnnn processes are slave processes dynamically spawned by SMCO to perform space management tasks in the background. These tasks include preallocating space into locally managed tablespace and SecureFiles segments based on space usage growth analysis, and reclaiming space from dropped segments. At most 10 Wnnn slaves can run on one database instance. After being started, the slave acts as an autonomous agent. After it finishes task execution, it automatically picks up another task from the queue. The process terminates itself after being idle for a long time.
"
And
"SMCO is the master space management process that dynamically allocates and deallocates space. It spawns slave processes Wnnn to implement the tasks."
Theres a lovely note that explains very clearly what the SMCO is and how to turn it on and off,
SMCO (Space Management Coordinator) For Autoextend On Datafiles And How To Disable/Enable (Doc ID 743773.1)
So thats all good to here, the SMCO is amongst other things handling the autoextend on files. From that note, I can turn it on and off if I want (I dont really want to) but my main question is why would that be generating as much REDO as it is or at least how would I find out why?
How am I getting the REDO generated by session? I snap v$mystat on redo size every minute which gives me redo per session.