What is difference between optimistic and pessimistic concurrency?

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Tags

1. #locking
2. #control
3. #record
4. #prevents
5. #assumes
6. #users
7. #pessimistic
8. #worst
9. #actually
10. #matter
11. #because
12. #system
13. #update
14. #concurrency
15. #possibility
16. #conflicts
17. #unlikely
18. #called