If you are having trouble getting your head around the basics of Oracles Architecture, this video does a good job of simplifying things and making it easy to remember by breaking it down and describing it via everyday examples. You can skip to around 2:30 for the real start of the video. Notes; Datafiles – …
[embedplusvideo height=”328″ width=”584″ standard=”http://www.youtube.com/v/wmc9uxNW99E?fs=1″ vars=”ytid=wmc9uxNW99E&width=584&height=328&start=&stop=&rs=w&hd=0&autoplay=0&react=1&chapters=¬es=” id=”ep5503″ /] Check out part 1 first. Notes: Online Redo Logs Contains Redo and Undo info DML Inserts/Deletes DDL – Create alter drop Commits Need at least 2 files/groups Should be multiplexed each on different devices and controlers When each file fils, next one is started and old one is archived (if …
There is no function in Oracle (up to 11g currently) that will allow you to reduce the size of the undo tablespace. Sometimes you will need to free up space and the best way to get it will be to reduce the size of the undo tablespace. The way to do this is basically to …
When data is changed in the oracle database, the information needed to undo the changes is recorded so that the change can be undone (Rolled back). The record is basically just the original information. Information is recorded in rollback segments and the undo tablespaces. This information is also used to provide read consistency which allows long running transactions …
In Oracle, the Undo records allow data that is being modified to be accessed. Oracle uses row level locking to prevent two processes from trying to update the same data at the same time. Only the rows being modified are locked. This means that the rest of the table can still be modified while a …