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Oracle Online Features - Golfing Instead of Working on Weekends

Explore Oracle's online features that allow you to perform tasks such as creating/rebuilding indexes, validating structure, and redefining tables without interrupting your weekend plans. Save time and enjoy golfing instead of working!

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Oracle Online Features - Golfing Instead of Working on Weekends

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  1. Oracle Online Features - Golfing Instead of Working on Weekends Oracle World 2003 – Session 36769 Sep 2003 Denny WongConsultantDatabase Services

  2. Introduction Take a system outage at 7pm on a weekday? No, because … • Internet applications • Nightly batch jobs • Users from other countries • 7x24 retail systems • Users work late during month-end • so on ...

  3. Introduction As a Result ... • You must work on the weekend • Well, you can still go golfing on the weekend because … • The regular system outage is between 1am - 5am on Saturday

  4. Introduction Oracle9i Online Features • Create/Rebuild Indexes Online • ALTER TABLE/INDEX VALIDATE STRUCTURE ONLINE • ALTER INDEX REBUILD COMPUTE STATISTICS ONLINE • Dynamic SGA • Online Table Redefinition

  5. Oracle9i (Enhancements) Create/Rebuild Indexes Online • Oracle extended these capabilities in 9i • Reverse-key index • Function-based index • Key-compressed index • IOT secondary index • Limitations • Parallel DML not supported while the index is being rebuilt • Bitmap and Cluster indexes can’t be rebuilt online

  6. Oracle9i (Enhancements) ANALYZE TABLE VALIDATE STRUCTURE ONLINE • Users can still perform DML on the table • ANALYZE TABLE VALIDATE STRUCTURE ONLINE • Verify the integrity of data blocks/rows (e.g. rows belong to the correct partition)

  7. Oracle9i (Enhancements) ANALYZE INDEX VALIDATE STRUCTURE ONLINE • Verify the structure of the index (e.g. Check block corruption) • When to rebuild an index? Cannot use the ONLINE option • SELECT DEL_LF_ROWS / LF_ROWS “Wasted” FROM INDEX_STATS • Rebuild the index If “Wasted” > 0.2, or • If index node utilization < 60% (PCT_USED < 60)

  8. Oracle9i (Enhancements) ALTER INDEX REBUILD COMPUTE STATISTICS ONLINE • An index should be analyzed after it has been rebuilt. • “ALTER INDEX REBUILD ONLINE” followed by “ANALYZE INDEX” • “ALTER INDEX REBUILD COMPUTE STATISTICS” • But, users cannot perform DML on the table • “ALTER INDEX REBUILD COMPUTE STATISTICS ONLINE” is available in Oracle9i • Users can perform DML on the table

  9. Oracle9i (New Features) Dynamic SGA • In database tuning, it may require adjusting the buffer cache or shared pool size • Requires an instance restart, challenging for 7x24 systems • Dynamic SGA components • Buffer cache (DB_CACHE_SIZE) • Shared pool (SHARED_POOL_SIZE) • Large pool (LARGE_POOL_SIZE) in Oracle9i Release 2

  10. Oracle9i (Dynamic SGA) • E.g., increase the buffer cache size from 32M to 64M dynamically

  11. Oracle9i (Dynamic SGA) SGA_MAX_SIZE • SGA is basically made up of memory components, such as buffer cache, shared pool, large pool, java pool, etc ... • SGA_MAX_SIZE limits the maximum size the SGA can grow dynamically

  12. Oracle9i (Dynamic SGA) SGA_MAX_SIZE • Example • SGA_MAX_SIZE = 208M • Sum of all memory components = 200M • Increase the shared pool by another 16M will fail because there is only 8M (208M - 200M) available

  13. Oracle9i (Dynamic SGA) Granule • A piece of contiguous memory that Oracle allocates in SGA • If SGA < 128M, the granule size will be 4M otherwise it will be 16M • Oracle allocates space in SGA by multiples of granules • V$SGA views containing Dynamic SGA information … next slide -->

  14. Oracle9i (Dynamic SGA) V$SGA • V$SGA_DYNAMIC_COMPONENTS • Dynamic SGA component name, size, granule size, etc … • V$SGA_DYNAMIC_FREE_MEMORY • Amount of SGA memory can be grown dynamically • V$SGA_CURRENT_RESIZE_OPS • SGA resize operations currently in progress • V$SGA_RESIZE_OPS • Last 100 SGA resize operations

  15. Oracle9i (Online Table Redefinition) Online Table Redefinition • Allows you to redefine a table structure while users are performing DML on the table • Online Table Redefinition Capabilities • Reorganize a table • Drop/add columns • Change a heap (regular) table to an IOT • Change a non-partitioned table to a partition table • So on ...

  16. Oracle9i (Online Table Redefinition) Online Table Redefinition • The whole redefinition process involves a number of DBMS_REDEFINITION procedure calls • CAN_REDEF_TABLE – Check if the table can be redefined • START_REDEF_TABLE – Start the redefinition process • SYNC_INTERIM_TABLE – Synchronize data modifications (Optional) • FINISH_REDEF_TABLE – Finish the redefinition process • ABORT_REDEF_TABLE – Abort the redefinition process

  17. Oracle9i (Online Table Redefinition) Steps for Redefining a Table Online • How to redefine a table online? Let’s walk through an example … • Reorganize table EMPLOYEE and drop column OLD_SALARY • Step 1) Verify the Table • Step 2) Create the Interim Table • Step 3) Start the Redefinition Process • Step 4) Create Indexes, Constraints, Triggers and Grants on the Interim Table • Step 5) Complete the Redefinition Process • Step 6) The Final Step

  18. Oracle9i (Online Table Redefinition) • Step 1) Verify the Table • Limitations of Online Table Redefinition. The table ... • must have a primary key (prior to Oracle9i Release 2) • must not contain any LONG or FILE columns • cannot have any materialized view defined on it • must be defined within the same schema • Execute the CAN_REDEF_TABLE procedure to verify • If the table cannot be redefined, it will raise an error

  19. Oracle9i (Online Table Redefinition) • Step 2) Create the Interim Table • The interim table will ultimately become the new table • All desired table definitions must be defined on the interim table • However indexes, constraints and triggers will be created later in step 4 • In our example, we will reorganize table EMPLOYEE and drop column OLD_SALARY • continue …

  20. Oracle9i (Online Table Redefinition)

  21. Oracle9i (Online Table Redefinition) • Step 3) Start the Redefinition Process • Execute the START_REDEF_TABLE procedure • It will create a materialized view and log • The log keeps track of any data modifications made by users • Then, it starts copying the data from EMPLOYEE to INTERIM • continue …

  22. Oracle9i (Online Table Redefinition) • If the original and interim table have different columns • Then, specify all the column names when calling the procedure

  23. Oracle9i (Online Table Redefinition) • Step 4) Create Indexes, Constraints, Triggers and Grants on the Interim Table • Create after START_REDEF_TABLE is completed • What we define on the interim table will ultimately belong to the new table • Foreign key constraints must be created in disabled state

  24. Oracle9i (Online Table Redefinition) • Step 5) Complete the Redefinition Process • Execute the FINISH_REDEF_TABLE procedure • Data Synchronization • Any data modifications recorded in the materialized log will be transferred to INTERIM • Switch Tables • EMPLOYEE will be locked • Switch the table names of EMPLOYEE and INTERIM • Drop the materialized view and log • continue ...

  25. Oracle9i (Online Table Redefinition)

  26. Oracle9i (Online Table Redefinition) • Step 6) The Final Step • EMPLOYEE has been redefined successfully • INTERIM is now the old copy of EMPLOYEE • Drop it to free up the space • Rename indexes, constraints and triggers on the new table • Rename index INTERIM_INDX created in step 4 • In Oracle9i Release 2, constraints and column names can be renamed • continue ...

  27. Oracle9i (Online Table Redefinition) • Users are accessing the new EMPLOYEE table (without OLD_SALARY) • The whole table redefinition process is now completed

  28. Oracle9i (Online Table Redefinition) • Synchronize Data Modifications (Optional) • Execute the SYNC_INTERIM_TABLE procedure • This procedure can be executed many times between START_REDEF_TABLE and FINISH_REDEF_TABLE • It propagates data modifications recorded in the materialized view log to the interim table • e.g. Execute SYNC_INTERIM_TABLE to propagate 5 million records to the interim table before creating the index • continue ...

  29. Oracle9i (Online Table Redefinition) • This synchronization is part of FINISH_REDEF_TABLE • Calling SYNC_INTERIM_TABLE doesn’t affect the short period of time the original table is locked

  30. Oracle9i (Online Table Redefinition) • Abort the Redefinition Process (if necessary) • E.g. You made a typo in the column name, or the tablespace ran out of space • Execute the ABORT_REDEF_TABLE procedure • The procedure will drop the materialized view and log • Re-start the redefinition process when the problem is fixed

  31. Conclusion • Oracle9i extended these online capabilities • Create/Rebuild Indexes Online • Reverse-key, function-based and key-compressed indexes • ALTER TABLE/INDEX VALIDATE STRUCTURE ONLINE • Examine the table/index without locking the table • ALTER INDEX REBUILD COMPUTE STATICS ONLINE • Rebuild the index and collect statistics without locking the table

  32. Conclusion • Dynamic SGA • Adjust buffer cache, shared pool and large pool dynamically • SGA_MAX_SIZE limits the maximum size the SGA can grow dynamically • Oracle allocates space in SGA by multiples of granules • Online Table Redefinition • Online capabilities • Reorganize a table • Change a heap table to IOT • Change a non-partitioned table to a partitioned table …

  33. Conclusion • Online Table Redefinition • A number of procedure calls to redefine a table online • CAN_REDEF_TABLE • START_REDEF_TABLE • SYNC_INTERIM_TABLE • FINISH_REDEF_TABLE • Create indexes, constraints and triggers on the interim table • Rename indexes, constraints and triggers on the new table

  34. Questions? Oracle Online Features – Golfing Instead of Working on Weekends Session 36769 Denny Wong Denny.Wong@cgi.com • Reference Sources • Experience • Oracle Metalink • Oracle Technet

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