2. PASS Community Summit - Seattle November 18-22, 2002 S231/S348 - Resolving Deadlocks in SQL Server 2000 Ron Talmage - Prospice, LLC

6. Lock-Based Deadlocking Structure GRANT T3 Request(WAIT on Tran1) T5 Blocked (blocking removed) Deadlock Victim T6 Commit T7 Request (WAIT on Tran2) T4 Blocked GRANT T2 Begin Tran Begin Tran T1 Tran 2 Tran 1 Time

7. Deadlocking Illustrated Thread 1 Thread 2 Grant Wait Blocked request Resource Resource

14. 1. Lock Modes Used with bulk copy into a table with either TABLOCK hint or table lock option is set BU Bulk Update Have update lock with intent to acquire exclusive lock at a finer level UIX Update Intent Exclusive Have shared lock with intent to acquire exclusive lock at a finer level SIX Shared Intent Exclusive Have shared lock with intent to acquire update lock at a finer level SIU Shared Intent Update Have or intend to request exclusive lock(s) at a finer level IX Intent Exclusive Have or intend to request update lock(s) at a finer level IU Intent Update Have or intend to request shared lock(s) at a finer level IS Intent Shared Used for writing (insert, update, delete) X Exclusive Used to evaluate prior to writing (may become exclusive) U Update Used for reading (read lock) S Shared Used for DDL operations (ALTER or DROP) on a table schema Sch-M Schema Modification Used when compiling queries Sch-S Schema-Stability Description Abbreviation Lock Mode

15. Lock Compatibility Matrix (default isolation level) Lock Mode Already Granted BU Sch-M Sch-S X SIX IX U S IS Lock Mode Requested No No Yes No Yes Yes Yes Yes Yes IS No No Yes No No No Yes Yes Yes S No No Yes No No No No Yes Yes U No No Yes No No Yes No No Yes IX No No Yes No No No No No Yes SIX No No Yes No No No No No No X Yes No Yes No No No No No No BU No No No No No No No No No Sch-M Yes No Yes Yes Yes Yes Yes Yes Yes Sch-S

19. Isolation Level and Lock Accumulation Held until end of transaction Held until end of transaction unless promoted to exclusive or released Held until data read and processed Read Un-committed Held until end of transaction Held until end of transaction unless promoted to exclusive Held until end of transaction Repeatable Read Held until end of transaction Held until end of transaction Exclusive Held until end of transaction unless promoted to exclusive Held until end of transaction unless promoted to exclusive or released Update Held until end of transaction Held until data read and processed Shared Serializable Read Committed Lock Mode

23. Single-Resource Deadlock Illustrated Resource Thread 1 Thread 2 Grant Wait Blocked request

24. Single-Resource Deadlock Select * From Authors With (HOLDLOCK) Where au_id = '172-32-1176' T3 GRANT Update Authors Set contract = 1 Where au_id = '172-32-1176' T5 Blocked (blocking removed) Deadlock Victim T6 Commit T7 Update Authors Set contract = 0 Where au_id = '172-32-1176' T4 Blocked Select * From Authors With (HOLDLOCK) Where au_id = '172-32-1176' T2 GRANT Begin Tran Begin Tran T1 Tran 2 Tran 1 Time

27. MR Deadlock Illustrated Res 1 Thread 1 Thread 2 Res 2 Grant Wait Blocked request

29. X-only MR Deadlock Update Titles Set ytd_sales = 0 Where title_id = ‘BU1032' T3 GRANT Update Authors Set contract = 0 Where au_id = '172-32-1176' T5 Blocked (blocking removed) Deadlock Victim T6 Commit T7 Update Titles Set ytd_sales = 0 Where title_id = ‘BU1032' T4 Blocked Update Authors Set contract = 0 Where au_id = '172-32-1176' T2 GRANT Begin Tran Begin Tran T1 Tran 2 Tran 1 Time

32. Mixed X-S MR Example #1 Update Titles Set ytd_sales = 0 Where title_id = ‘BU1032' T3 GRANT Select * From Authors Where au_id = '172-32-1176' T5 Blocked (blocking removed) Deadlock Victim T6 Commit T7 Select * From Titles Where title_id = ‘BU1032' T4 Blocked Update Authors Set contract = 0 Where au_id = '172-32-1176' T2 GRANT Begin Tran Begin Tran T1 Tran 2 Tran 1 Time

33. Mixed X-S MR Example #2 Insert Authors Values ('111-11-1112', 'test2', '', '', '', '', '', '11111', 0) T3 GRANT Select * From Authors T5 Blocked (blocking removed) Deadlock Victim T6 Commit T7 Select * From Authors T4 Blocked Insert Authors Values ('111-11-1111', 'test1', '', '', '', '', '', '11111', 0) T2 GRANT Begin Tran Begin Tran T1 Tran 2 Tran 1 Time

38. Adding the Deadlock Counter

47. Viewing Deadlocks in Profiler Deadlock spids now cross-referenced in SP2

52. Extracting a Transaction History

53. Reproducing the Deadlock

55. Identifying the query

56. Identifying the locks KEY: 7:1977058079:1 (f600d547433a) (from trace flag 1204 output)

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