New bie Information of redo and datafile

Hello All,

Good Morning!,
Hope every one is doing good.

I have a very simple two questions:-

1. If I issue a sql statement to insert value or delete value or modify the value in the table. What exact information goes in the redolog file and datafile. I know that redo entries goes in the redolog file, but I need to know what exactly get stored in the redolog file and datafile.
2. Suppose a dba gets a pager that datafile threshold has reached 90% and he goes and add a datafile . How does oracle comes to know that after the current datafile is full it needs to store the data in the new datafile added.

Thanks
Nilesh

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