I Didn't Know DB2 Did THAT! V9 & V10 Update CENTRAL CANADA DB2 USER GROUP

Transcription

1 I Didn't Know DB2 Did THAT! V9 & V10 Update CENTRAL CANADA DB2 USER GROUP Bonnie K. Baker Bonnie Baker Corporation

2 INTERNAL MYSTERIES SOLVED 2

3 Internal Mysteries Solved DB2 PROGRAM PREPARATION LATCHES & LATCH SUSPENSIONS X 3 EDMPOOL - 1 BUFFERPOOLS - 2 CLAIMS & DRAINS GETPAGE VS. READ IO DATA MANAGER vs. RDS ORDER OF PREDICATE APPLICATION DBD CHAINS SIX LOCKS RELEASE BIND PARAMETER RANDOM INDEXES & SORT AVOIDANCE AVOIDING YOUR OWN NEWLY INSERTED ROWS 3

4 Program Execution SELECT... INTO Host Variables SQLCA SSAS DBAS LMAS MSTR DBM1 IRLM EDMPOOL SORTPOOL LOG PLAN PKG WORKING STORAGE DBDs DSC RDS DATA MGR GETPAGE LOCK? RIDPOOL BUFFERPOOL? BUFFER MGR LATCH? Directory Catalog Workspace DSNDB01 DSNDB06 DSNDB07 Tables Indexes 4

5 PROGRAM PREPARATION PROCESS SOURCE CODE INCLUDE LIBRARY PRECOMPILE MODIFIED SOURCE CODE SQL IN DBRM in LIBRARY COMPILE LINK BIND PACKAGE REBIND PACKAGE LOAD MODULE IN LOADLIB DIRECTORY PACKAGE CATALOG DBRM 5

6 Internal Mysteries Solved LATCHES ON EDMPOOL MRU/LRU CHAIN BUFFERPOOL MRU/LRU CHAIN BUFFERPOOL INDEX PAGES BUFFERPOOL TABLE PAGES 6

7 Internal Mysteries Solved EDMPOOL PLANS PACKAGES PACKAGE SEGMENTS: BASE + SPACE MANAGEMENT TECHNIQUE MRU/LRU CHAIN NON-STEALABLE STEALABLE (MRU/LRU) FREE BASE PKGA BASE PKG3 BOB S SUE S PKGA JOE S SEG7 SEG7 SEG7 SEG7 7

8 Internal Mysteries Solved BUFFERPOOL MRU/LRU CHAIN BUT - TWO SPACE MANAGEMENT TECHNIQUES MRU/LRU WITH LATCHES PGSTEAL (FIFO) WITHOUT LATCHES? NON-STEALABLE STEALABLE FREE WHEN IS FIFO APPROPRIATE? 8

9 Internal Mysteries Solved BUFFERPOOL INDEX PAGE & TABLE PAGE LATCHES S OR X WHY LATCH? WITH UR? OK TO READ DURING UPDATE? WITH CS? ENSURES STABLE (NOT CLEAN) DATA ALLOWS READ OF PAGES WITH X LOCKS DURATION? Acquired? Released? 9

10 Internal Mysteries Solved BUFFERPOOL MANAGER ALSO WORKS WITH VSAM FOR READ IO ALSO HANDLES CLAIMS & DRAINS CLAIM COUNTERS FOR SQL READ COUNTER WRITE COUNTER DRAIN NEGOTIATION BY UTILITIES 10

11 Internal Mysteries Solved DATA MANAGER GETPAGE requests MRU/LRU Latch included in cost Page addressing BP is addressable working storage Update Before & After comparisons New V10 relief with Indicators Accesses DBD for cheat sheet information What is a DBD? 11

12 Internal Mysteries Solved DATA MANAGER - continued Stage 1 Predicates Applied by the Data Manager Indexable (Matching & Screening) Not Indexable RDS Stage 2 Predicates Done by RDS, not Data Manager Indexable (V10 Screening) Not Indexable 12

13 ORDER OF PREDICATE APPLICATION V9 & PRIOR 1. STAGE 1 INDEX-MATCHING PREDICATES 2. STAGE 1 INDEX-SCREENING PREDICATES applied in the order of the index columns 3. STAGE 1 OTHER PREDICATES APPLIED TO TABLE EQUAL PREDICATES RANGE PREDICATES, IS NULL, IS NOT NULL IN, LIKE PREDICATES EACH GROUP IN ORDER CODED 4. STAGE 2 PREDICATES APPLIED TO TABLE ASSUME AN INDEX ON LASTNAME, FIRSTNAME, MIDDLE_INIT, EMPID, MGRID WHERE 7 SAL + COM > AND FIRSTNAME = ELIZABETH 3 AND MIDDLE_INIT = K 1 AND LASTNAME = BAKER 4 AND HAIR_COLOR = BROWN 6 AND SALARY > = AND EYE_COLOR = BLUE 8 AND EMPID MGRID = :HV1 :HV2 13

14 ORDER OF PREDICATE EVALUATION IN V10 STAGE 1 INDEX-MATCHING PREDICATES STAGE 1 INDEX-SCREENING PREDICATES STAGE 2 INDEX-SCREENING PREDICATES STAGE 1 OTHER PREDICATES APPLIED TO TABLE STAGE 2 PREDICATES APPLIED TO TABLE applied in the order of the index columns EQUAL PREDICATES RANGE PREDICATES, IS NULL, IS NOT NULL IN, LIKE PREDICATES EACH GROUP IN ORDER CODED ASSUME AN INDEX ON LASTNAME, FIRSTNAME, MIDDLE_INIT, EMPID, MGRID WHERE 8 SAL + COM > AND FIRSTNAME = ELIZABETH 3 AND MIDDLE_INIT = K 1 AND LASTNAME = BAKER 5 AND HAIR_COLOR = BROWN 7 AND SALARY > = AND EYE_COLOR = BLUE 4 AND EMPID MGRID = :HV1 :HV2 14

15 Internal Mysteries Solved DATA MANAGER - continued LOCK REQUESTS CROSS-MEMORY SERVICES CALLS TO IRLM CALLS AT ACQUISITION & RELEASE) RELEASE WHEN? IS OR IX? IS OR IX? S? S? S? S? U? U? U? U? X? X? X? X? 15

16 Internal Mysteries Solved DATA MANAGER - continued DB2 RI ENFORCEMENT CHOOSES ACCESS PATHS AT RUNTIME USES DBD INFORMATION DECLARED TEMP TABLE ACCESS GATHERS STATISTICS DETERMINES ACCESS PATHS AT RUNTIME 16

17 Optimizer Magic Explained SIX LOCKs Huge maintenance program Only program allowed to do maintenance Others can read WITH UR or IS on TSP IS on TBL S (or no lock) on PAGE 17

18 Optimizer Magic Explained SIX LOCKs continued MAINTENANCE PROGRAM: LOCK TABLE T1 in SHARE MODE 1 st read gets IS on TSP + S on TBL 1 st UPDATE gets X on page upgrades S on TBL to SIX upgrades IS on TSP to IX 18

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20 Program Logic Fun TABLESPACE, PARTITION, & TABLE LOCKS + Release COMMIT/DEALLOCATE What happens at COMMIT? IF LOCK TABLE STATEMENT? + If RELEASE(COMMIT)? If RELEASE(DEALLOCATE)? 20 New with Java in V10 RELEASE DEALLOCATE 20

21 SQL Tricks Shared GROUP BY + ORDER BY? Both needed? If on different columns? Of course But what if same columns? GROUP BY WKDEPT ORDER BY WKDEPT Multiple indexes on same columns? With different asc/desc options Impact of New RANDOM Index option 21

22 Program Logic Fun Avoiding your own newly Inserted rows Force Sort? Declared/Created Temp Table? Sensitive Static Scroll Cursor? Insensitive Static Scroll Cursor? Better Solution? Disqualify your new rows in your cursor WHERE clause 22

23 SUMMARY Internal Mysteries Solved Optimizer Magic Explained SQL Tricks/Oddities Shared Program Logic Fun 23

24 Bonnie K. Baker Bonnie Baker Corporation THANK YOU