The document provides an overview of the fb_lock_print utility and the lock manager in Firebird, covering the types of locks, their usage, and features such as deadlock detection and monitoring. It discusses internal vs external locks, different lock types and states, and tuning options for the lock manager. Additionally, it includes details on configuring the lock manager and using the lock print utility for monitoring and output control.

1. Understanding the lock manager with the fb_lock_print utility Dmitry Yemanov mailto:dimitr@firebirdsql.org Firebird Project http://www.firebirdsql.org/

2. Synchronization in Firebird Internal vs external locks Mutexes, spinlocks, RW locks, latches

3. Lock manager Features of the global locks Multiple states (SR, PR, SW, PW, EX)

4. Blocking notifications

5. Deadlock detection

6. Monitoring abilities

7. Lock Types and their Usage Lock types Database lock

8. Existence locks (table, procedure, index, collation)

9. Table access locks

10. Transaction locks

11. Sweep, shadow, monitoring, etc locks Page locks (!)

12. Lock Types and their Usage Lock types LCK_database = 1 // Root of lock tree LCK_relation = 2 // Individual relation lock LCK_bdb = 3 // Individual buffer block LCK_tra = 4 // Individual transaction lock LCK_rel_exist = 5 // Relation existence lock LCK_idx_exist = 6 // Index existence lock LCK_attachment = 7 // Attachment lock ...

13. Locks and Firebird Architectures SuperServer No page locks

14. Small lock table

15. Fast LM operations Classic and SuperClassic Page locks are widely used

16. Large lock table

17. LM operations may require IPC

18. Lock Manager in Classic IPC IPC IPC Connection 1 Connection 2 fb_inet_server fb_inet_server fb_lock_mgr Lock table (shmem)

19. Inside the Lock Table Block types Header section

20. Lock owners

21. Lock resources

22. Lock requests Internals Single mutex around the shmem region

23. Remappings

24. Hash table of lock keys

25. Inside the Lock Table Lock resource Series: page lock Key: 01:75 State: PR Lock request 1 PR (granted) Lock request 3 EX (pending) Lock request 4 EX (pending) Owner 1 PID = 1008 Owner 3 PID = 870 Owner 4 PID = 114 Lock request 2 PR (granted) Owner 2 PID = 788

26. Inside the Lock Table Owner states Waiting = 0x4

27. Signaled = 0x10 Request states Pending = 0x2

28. Blocking = 0x1

29. Blocking seen = 0x100

30. Tuning the Lock Manager Configuration options LockMemSize (1MB) ~= <cache pages> * <max connections> * 100

31. LockSemCount (32) – deprecated in v2.5

32. LockHashSlots (1009) Other considerations FIREBIRD_LOCK envvar

33. Using the Lock Print Utility Output control switches -o [wners]

34. -l [ocks]

35. -r [equests]

36. -s [eries] <number>

37. -a [ll]

38. -w [ait list] Default output Header and owners only

39. Using the Lock Print Utility Interactive mode -i [aotw] <number> <number>

40. Acquires, operations, types, waits

41. Seconds and intervals Other options -c

42. -d <database> or -f <lock file>

43. -m

44. Questions?