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Locally Managed Tablespaces in Oracle8 i

Locally Managed Tablespaces in Oracle8 i. Raghav Vinjamuri rvinjamuri@yahoo.com. Questions. Extents Size of Individual Extent in a Segment Matters/Does Not Matter? Number of Extents Matters/Does Not Matter?. Questions ( AND Answers). Extents Size of Individual Extent in a Segment

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Locally Managed Tablespaces in Oracle8 i

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  1. LocallyManaged TablespacesinOracle8i Raghav Vinjamuri rvinjamuri@yahoo.com

  2. Questions • Extents • Size of Individual Extent in a Segment • Matters/Does Not Matter? • Number of Extents • Matters/Does Not Matter?

  3. Questions ( AND Answers) • Extents • Size of Individual Extent in a Segment • Matters/Does Not Matter? • if small, can lead to numerous extents. • Number of Extents • Matters/does not matter? • Due to overheads of dictionary maintenance, May not be for full table scan performance.

  4. Questions ( AND Answers) • Extent Management • Extents must therefore be • Fixed Size - Appropriately Large, • Fixed in Number • How to implement/manage Fixed Size Extents in an Oracle database?

  5. Overview • Extent Management • Dictionary Managed Tablespaces - “DMT” • Locally Managed Tablespaces - “LMT” • Features/“Bugs”/“Usage Quirks” of LMTs in Oracle8i Rel 8.1.6.0 • Benefits of LMTs over DMTs • Summary & References • Q&A

  6. Extent Management • How to implement Fixed Size Extentsin an Oracle database? • Pre-Oracle8 • Oracle8 • Oracle8i

  7. Extent Management • Pre-Oracle8 • DEFAULT STORAGE • INITIAL and NEXT are set equal, and • PCTINCREASE=0 • Caveats • Extent Sizes Rounded Up. • Nearest Multiple of 5. • MAYBE more (up to 4 additional blocks) if there are fewer than 5 blocks remaining in the unallocated portion. • Coalescing of Free Extents by SMON. • Extent Trimming After Parallel Operations.

  8. Extent Management • Oracle8 • DEFAULT STORAGE • INITIAL and NEXT are set equal, and • PCTINCREASE=0 • MINIMUM EXTENT integer • the minimum size of an extent in a tablespace. • controls free space fragmentation in tablespaces • ensures every used/free extent size in a tablespace is at least as large as, and is a multiple ofinteger • eliminates unwarranted extent size rounding/trimming

  9. Extent Management • Dictionary ManagedTablespaces “DMT” • Free/Used Extent information of tablespaces tracked via Data Dictionary Tables (FET$ and UET$) • differentiates from Locally Managed Tablespaces in Oracle8i

  10. Locally Managed Tablespaces • New in Oracle8i • EXTENT MANAGEMENT LOCAL clause of CREATE TABLESPACE statement • EXTENT MANAGEMENT DICTIONARY still is Default. • Allows Fixed Extent Size(s) • AUTOALLOCATE or “System Determined” Sizes • UNIFORM Size

  11. Locally Managed Tablespaces • Create Tablespace TESTLMT datafile ‘lmt01.dbf’ size 1000M reuse EXTENT MANAGEMENT LOCALAUTOALLOCATE; • Create Tablespace TESTLMT datafile ‘lmt01.dbf’ size 1000M reuse EXTENT MANAGEMENT LOCALUNIFORM Size 10M;

  12. Locally Managed Tablespaces • AUTOALLOCATE • is default • can specify initial extent and Oracle determines the size of the rest, with a minimum of 64k • UNIFORM • default is 1MB

  13. Locally Managed Tablespaces • Summary Notes for DBA’s 1. LMTs and DMTs can co-exist in same DB. 2. EXTENT MANAGEMENT DICTIONARY is default. 3. Currently, a locally managed SYSTEM tablespace (?? For ROLLBACK SEGMENT usage) cannot be created (True in 8.1.7) 4. EXTENT MANAGEMENT LOCAL • CREATE TABLESPACE statement - for permanent tablespaces • CREATE TEMPORARY TABLESPACE statement - for temporary tablespaces

  14. Locally Managed Tablespaces • Summary Notes for DBA’s … 2 • CREATE TEMPORARY TABLESPACE statement - for temporary tablespaces CREATE TEMPORARY TABLESPACE TEMP TEMPFILE 'temp.dbf' SIZE 256M EXTENT MANAGEMENT LOCAL UNIFORM SIZE 256K; 5. When creating an LMT, AUTOALLOCATE is default. 6. Temporary LMT’s can only use UNIFORM SIZE, and not AUTOALLOCATE.

  15. Locally Managed Tablespaces • Summary Notes for DBA’s … 3 7. Parameters • TEMPORARY, • MINIMUM EXTENT, or • DEFAULT storage_clause, • NEXT, • PCTINCREASE, • MINEXTENTS, • MAXEXTENTS are not valid for locally managed tablespaces. Could get an error or be silently ignored!!

  16. Locally Managed Tablespaces • Summary Notes for DBA’s … 4 8. DBMS_SPACE_ADMIN package provides • Defect Diagnosis and Repair Functionality for LMT • Migration of DMT to LMT or vice-versa 9. LMTs can be altered for many of the same reasons as a dictionary-managed tablespace. However, • altering storage parameters is not an option and • coalescing free extents is unnecessary • an LMT cannot be altered to a locally managed temporary tablespace.

  17. Locally Managed Tablespaces • Summary Notes for DBA’s … 5 10. To find out which tablespaces are LMTs • SELECT tablespace_name, extent_managementFROM dba_tablespacesWHERE extent_management = 'LOCAL';

  18. These slides (and, a white paper!) will be posted on the NOCOUG web site, athttp://www.nocoug.org

  19. Questions ?

  20. Good Luck!

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