What is commit_delay & commit_siblings?

[laconicamit]

Can anyone please tell me the impact of uncommenting these two parameters of postgresql.conf ig file.

#commit_delay = 0 # range 0-100000, in microseconds
#commit_sibling s = 5 # range 1-1000

And is there any, auto commit setting can be done thru this?

[michaelb]

Both settings have to do with WAL - Write Ahead Log.
You can read more about these and other WAL configuration parameters here and here

Auto-commit, I believe is always ON by default.
I think there used to be a server-side autocommit option, but it was taken out in some earlier release, so you may need to use transactions to control this behavior.