Indexes and Indexing in Oracle 12c
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The document provides an overview of indexing features in Oracle 12c, including multiple indexes on the same column, extended string capabilities, and online DDL operations. It discusses asynchronous global index maintenance, partial indexes, and advanced index compression techniques. The presentation emphasizes the importance of thorough testing and licensing before implementing these features in production environments.
![This presentation is available in http://db-oriented.com/presentations
©OrenNakdimon
WHO AM I?
A CHRONOLOGY BY “ORACLE YEARS”
When What Where
Oracle 6/7 1991-1997 Developer IAF
Oracle 8 1997-1998 Server Group Manager Golden Screens
Oracle 8i/9i 1998-2003 DBA Group Manager TELEknowledge
Oracle 10g/11g 2004-2011 VP R&D and
Israel Site Manager
Olista
Oracle 11g/12c 2011-2015 Freelance Consultant
2015- Database Expert
http://www.db-oriented.com/blog [English]
http://www.db-oriented.com/blog-2 [Hebrew]](https://image.slidesharecdn.com/orennakdimon-12cindexesnewfeatures-170218092214/85/Indexes-and-Indexing-in-Oracle-12c-2-320.jpg)
Indexes and Indexing in Oracle 12c
- 1. INDEXES AND INDEXING IN ORACLE 12C © Oren Nakdimon Oren Nakdimon www.db-oriented.com [email protected] +972-54-4393763 @DBoriented
- 2. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon WHO AM I? A CHRONOLOGY BY “ORACLE YEARS” When What Where Oracle 6/7 1991-1997 Developer IAF Oracle 8 1997-1998 Server Group Manager Golden Screens Oracle 8i/9i 1998-2003 DBA Group Manager TELEknowledge Oracle 10g/11g 2004-2011 VP R&D and Israel Site Manager Olista Oracle 11g/12c 2011-2015 Freelance Consultant 2015- Database Expert http://www.db-oriented.com/blog [English] http://www.db-oriented.com/blog-2 [Hebrew]
- 3. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon AGENDA Multiple indexes on the same column list Indexes and extended strings Online operations Asynchronous global index maintenance Partial indexes Advanced index compression
- 4. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon THE USUAL WARNING Before you decide to apply any of the presented features in production, make sure: to thoroughly test them for your applications and environments that you have the required license to use them
- 5. Multiple Indexes on the Same Column List
- 6. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon INVISIBLE INDEXES (11G) An invisible index is: Maintained by DML Invisible to the optimizer Unless optimizer_use_invisible_indexes is true @iind
- 7. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon MULTIPLE INDEXES ON THE SAME COLUMN LIST Before 12c Impossible to define several indexes on the same column list In 12c It is possible, as long as Only one of the indexes is visible The indexes are different somehow; for example: Unique vs. non-unique B*tree vs. bitmap Partitioned vs. non-partitioned @mind
- 9. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon EXTENDED STRINGS By default, maximum length of: VARCHAR2 and NVARCHAR2 columns is 4KB RAW columns is 2KB If MAX_STRING_SIZE = EXTENDED, it is 32KB Implemented like LOBs SQL string functions can return 32KB @32k
- 10. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon EXTENDED STRINGS – ENABLING MAX_STRING_SIZE can be changed from STANDARD to EXTENDED, but not from EXTENDED to STANDARD COMPATIBLE must be set to 12.0.0.0 or higher Can be done only in UPGRADE mode The script utl32k.sql must be executed Objects may be invalidated Instructions: http://docs.oracle.com/cloud/latest/db121/REF RN/refrn10321.htm
- 12. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon ONLINE DDL OPERATIONS In 12c more operations can be executed online: ALTER INDEX VISIBLE ALTER INDEX INVISIBLE DROP INDEX ONLINE ALTER INDEX UNUSABLE ONLINE ALTER TABLE MOVE SUB/PARTITION ONLINE @online1|2|3|4
- 13. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon ONLINE DDL OPERATIONS Offline Operations Online Operations
- 14. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon ONLINE DDL OPERATIONS Offline Operations Online Operations Get ORA-54 due to active transactions Wait for active transactions to end
- 15. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon ONLINE DDL OPERATIONS Offline Operations Online Operations Get ORA-54 due to active transactions Wait for active transactions to end Block new DML statements Do not block new DML statements
- 16. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon ONLINE DDL OPERATIONS Offline Operations Online Operations Get ORA-54 due to active transactions Wait for active transactions to end Block new DML statements Do not block new DML statements ALTER INDEX UNUSABLE drops the index segment ALTER INDEX UNUSABLE keeps the index segment
- 17. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon ONLINE DDL OPERATIONS Offline Operations Online Operations Get ORA-54 due to active transactions Wait for active transactions to end Block new DML statements Do not block new DML statements ALTER INDEX UNUSABLE drops the index segment ALTER INDEX UNUSABLE keeps the index segment MOVE PARTITION may lead to unusable indexes MOVE PARTITION keeps the indexes usable
- 19. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon ASYNC GLOBAL INDEX MAINTENANCE DROP/TRUNCATE PARTITION Before 12c: either fast operation or keeping global indexes usable In 12c: both fast operation and keeping global indexes usable New data dictionary column ORPHANED_ENTRIES Orphaned index entries are: Not deleted as part of the operation Not reused (usually) @async1
- 20. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon ASYNC GLOBAL INDEX MAINTENANCE Cleaning out the orphaned entries: Alter index rebuild Alter index coalesce cleanup DBMS_PART.CLEANUP_GIDX PMO_DEFERRED_GIDX_MAINT_JOB @async2
- 21. Partial Indexes
- 22. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon PARTIAL INDEXES In 12c it is possible to create an index on a subset of partitions Supported for both local and global indexes The optimizer is aware of it INDEXING ON | INDEXING OFF At table/partition level INDEXING PARTIAL At index level New data dictionary columns: INDEXING @pind
- 24. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon INDEX COMPRESSION CONCEPT CREATE INDEX PEOPLE_IDX ON PEOPLE (LAST_NAME,FIRST_NAME) Allen,Alex,rowid Allen,Barbara,rowid Allen,David,rowid Allen,James,rowid Allen,John,rowid Allen,Linda,rowid Allen,Mary,rowid Allen,Michael,rowid Allen,Patricia,rowid Allen,Robert,rowid Blake,David,rowid Blake,James,rowid Blake,Lisa,rowid Blake,Maria,rowid Blake,William,rowid #1=Allen #2=Blake #1,Alex,rowid #1,Barbara,rowid #1,David,rowid #1,James,rowid #1,John,rowid #1,Linda,rowid #1,Mary,rowid #1,Michael,rowid #1,Patricia,rowid #1,Robert,rowid #2,David,rowid #2,James,rowid #2,Lisa,rowid #2,Maria,rowid #2,William,rowid COMPRESS 1
- 25. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon INDEX COMPRESSION CONCEPT – CONT. Smith,Alex,rowid Smith,Alex,rowid Smith,Alex,rowid Smith,Alex,rowid Smith,Barbara,rowid Smith,Barbara,rowid Smith,Barbara,rowid Smith,Barbara,rowid Smith,Barbara,rowid Smith,David,rowid Smith,David,rowid Smith,David,rowid Smith,David,rowid Smith,David,rowid Smith,David,rowid #1=Smith #1,Alex,rowid #1,Alex,rowid #1,Alex,rowid #1,Alex,rowid #1,Barbara,rowid #1,Barbara,rowid #1,Barbara,rowid #1,Barbara,rowid #1,Barbara,rowid #1,David,rowid #1,David,rowid #1,David,rowid #1,David,rowid #1,David,rowid #1,David,rowid
- 26. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon INDEX COMPRESSION CONCEPT – CONT. Xa,Alex,rowid Xander,Barbara,rowid Xanders,David,rowid Xanthopoulos,Kevin,rowid Xanthos,Sandra,rowid Xavier,Sarah,rowid Xayachack,Scott,rowid Xayarath,Martin,rowid Xayasane,Donna,rowid Xayavong,Edward,rowid #1=Xa #2=Xander #3=Xanders #4=Xanthopoulos #5=Xanthos #6=Xavier #7=Xayachack #8=Xayarath #9=Xayasane #a=Xayavong #1,Alex,rowid #2,Barbara,rowid #3,David,rowid #4,Kevin,rowid #5,Sandra,rowid #6,Sarah,rowid #7,Scott,rowid #8,Martin,rowid #9,Donna,rowid #a,Edward,rowid @acmp
- 27. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon PREFIX INDEX COMPRESSION (SINCE ORACLE8I) Implemented in the leaf block level May reduce the size of the index Today’s optimal prefix length may be suboptimal tomorrow All the index blocks are compressed the same way
- 28. This presentation is available in http://db-oriented.com/presentations ©OrenNakdimon ADVANCED INDEX COMPRESSION Same mechanism, but: Each block may be compressed or not Each block may have different number of columns in the prefix table And it’s automatic
- 29. THANK YOU Oren Nakdimon www.db-oriented.com [email protected] +972-54-4393763 @DBoriented © Oren Nakdimon