what are the MAJOR areas you need to check when user facing some performance issues on oracle database?

we need to look into the below areas when you user reported  any performance issues on oracle database.

Below are the most of the common root cause for delay in SQL processing in database

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1.no proper stats for the sql

2.no proper indexing for the sql

3.lock while executing the sql

4.waits while executing the sql

5.more I/O while executing the sql

6.fragmentation on the objects of sql execution

7.due to poor memory configuration on database

8.due to library cache lock

9.could be locked /stale stats

10.could be poor resource on the server
11.check if any profiles disabled
12.check if any baseline modified
13.check the sql execution time for current and past dates