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Chapter 8 Advanced Table Management

Chapter 8 Advanced Table Management. Objectives. Create tables with large object (LOB) columns and tables that are index-organized Understand the tasks involved in table management Use data dictionary views to find information about tables and their underlying structures.

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Chapter 8 Advanced Table Management

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  1. Chapter 8 Advanced Table Management Oracle9i Database Administrator: Implementation and Administration

  2. Objectives • Create tables with large object (LOB) columns and tables that are index-organized • Understand the tasks involved in table management • Use data dictionary views to find information about tables and their underlying structures Oracle9i Database Administrator: Implementation and Administration

  3. Advanced Table Structures Table types covered: • Tables with LOB columns: • Store large amount of data in a single column of one row • Can define a separate segment for the LOB • Index-organized tables • Store data in primary key order • Best when queries nearly always use primary key to look up data in the table Oracle9i Database Administrator: Implementation and Administration

  4. Tables with LOB Columns Types of LOB columns: • Internal LOB • Stored inside the database • Datatypes: BLOB, CLOB, NCLOB • External LOB • Stored outside the database • Datatypes: BFILE • Read-only Oracle9i Database Administrator: Implementation and Administration

  5. Tables with LOB Columns Example: CREATE TABLE SOUNDBYTES (ALBUM_ID VARCHAR2(20), ARTIST VARCHAR2(40), CD_MUSIC BFILE, POSTER_SHOT BLOB ); External LOB Internal LOB Oracle9i Database Administrator: Implementation and Administration

  6. Tables with LOB Columns New package for updating internal LOBs: • DBMS_LOB.LOADBLOBFROMFILE: Load data into BLOB from external file • DBMS_LOB.LOADCLOBFROMFILE: Load data into CLOB from external file Co Oracle9i Database Administrator: Implementation and Administration

  7. Tables with LOB Columns Semantics of copying LOBs: • Internal LOB uses copy semantics: Copying a LOB from one row or column to another copies the contents • External LOB uses reference semantics: Copying a LOB from one row or column to another copies only a pointer to the original location of contents Co Oracle9i Database Administrator: Implementation and Administration

  8. LOB Storage • Internal LOBs: • Default stored inline or out of line, by size • Always stored out of line with DISABLE STORAGE IN ROW • External LOBs: • LOB locator stored in the table • LOB data stored in operating system file Oracle9i Database Administrator: Implementation and Administration

  9. LOB Storage Syntax: CREATE TABLE <tablename> (<other_column_specs>, <LOBcolumnname> <LOBdatatype>) LOB (<LOBcolumnname>) STORE AS <lobsegmentname> (TABLESPACE <tablespacename> ENABLE STORAGE IN ROW|DISABLE STORAGE IN ROW CHUNK <nn> STORAGE (INITIAL <nn> NEXT <nn> MAXEXTENTS UNLIMITED|<nn>) PCTVERSION <nn>|RETENTION LOGGING|NOLOGGING CACHE|NOCACHE); Oracle9i Database Administrator: Implementation and Administration

  10. LOB Storage Syntax of storage for LOB: • STORE AS <lobsegmentname> • DISABLE / ENABLE STORAGE IN ROWS • CHUNK <nn> • PCTVERSION / RETENTION • LOGGING / NOLOGGING • CACHE / NOCACHE Oracle9i Database Administrator: Implementation and Administration

  11. LOB Storage Example: Oracle9i Database Administrator: Implementation and Administration

  12. Index-Organized Tables • Relational table with primary key • Sorted and stored in key order • Normal relational tables are heap-organized • Stored in b-tree structure Oracle9i Database Administrator: Implementation and Administration

  13. Index-Organized Tables • Heap-organized versus Index-organized Oracle9i Database Administrator: Implementation and Administration

  14. Index-Organized Tables • Example: Oracle9i Database Administrator: Implementation and Administration

  15. Index-Organized Tables Syntax components: • ORGANIZATION INDEX • OVERFLOW • PCTTHRESHOLD • INCLUDING <col> • TABLESPACE <name> • STORAGE (<storage>) Oracle9i Database Administrator: Implementation and Administration

  16. Index-Organized Tables Example: CREATE TABLE ZIPREFERENCES (ZIPCODE VARCHAR2(10) NOT NULL, CITY VARCHAR2(40) NOT NULL, STATE VARCHAR2(10) NOT NULL, PROVINCE VARCHAR2(10) NOT NULL, COUNTRY VARCHAR2(20) NOT NULL, CONSTRAINT ZIP_PK PRIMARY KEY(ZIPCODE)) ORGANIZATION INDEX TABLESPACE USERS PCTTHRESHOLD 20 OVERFLOW TABLESPACE USERS STORAGE (INITIAL 64K NEXT 32K MAXEXTENTS 50 PCTINCREASE 0); Oracle9i Database Administrator: Implementation and Administration

  17. Overview of Table Management Types of changes: • Change the storage settings • Reorganize the table online • Drop columns • Truncate or drop the table Oracle9i Database Administrator: Implementation and Administration

  18. Analyzing a Table Why analyze tables? • To give the optimizer up-to-date information for optimizing queries and other SQL commands • To give you information to help you decide which storage or column settings to change Oracle9i Database Administrator: Implementation and Administration

  19. Analyzing a Table Oracle's optimizers: • Cost-based optimizer • Default • Uses table statistics • Rule-based optimizer • Older • Uses syntax rules only Oracle9i Database Administrator: Implementation and Administration

  20. Analyzing a Table Examples • ANALYZE command: ANALYZE TABLE CUSTOMER ESTIMATE STATISTICS SAMPLE 1000 ROWS; • DBMS_STATS package: EXECUTE DBMS_STATS.GATHER_TABLE_STATS - ('CLASSMATE','CUSTOMER'); Oracle9i Database Administrator: Implementation and Administration

  21. Adjusting Table Storage Structure Syntax of ALTER TABLE command: ALTER TABLE <schema>.<tablename> PCTFREE <nn> PCTUSED <nn> INITTRANS <nn> MAXTRANS <nn> STORAGE (NEXT <nn> PCTINCREASE <nn> MAXEXTENTS <nn>|UNLIMITED) ALLOCATE EXTENT SIZE <nn> DATAFILE <filename> DEALLOCATE UNUSED KEEP <nn> COMPRESS|NOCOMPRESS MOVE TABLESPACE <tablespacename> STORAGE (INITIAL <nn> NEXT <nn> PCTINCREASE <nn> MAXEXTENTS <nn>|UNLIMITED) COMPRESS|NOCOMPRESS ONLINE Oracle9i Database Administrator: Implementation and Administration

  22. Adjusting Table Storage Structure Syntax components: • PCTFREE <nn> PCTUSED <nn> • INITTRANS <nn> MAXTRANS <nn> • STORAGE (...) • ALLOCATE EXTENT • DEALLOCATE UNUSED • COMPRESS • MOVE • ONLINE Oracle9i Database Administrator: Implementation and Administration

  23. Adjusting Table Storage Structure Examples: • Deallocate unused space: ALTER TABLE HORSERACE DEALLOCATE UNUSED KEEP 50K; • Change STORAGE setting: ALTER TABLE CLASSIFIED_AD MOVE TABLESPACE USERS STORAGE (NEXT 56K); Oracle9i Database Administrator: Implementation and Administration

  24. Reorganizing a Table DBMS_REDEFINITION package: • Redefine anything in the table • Keep old version of the table available during the change Oracle9i Database Administrator: Implementation and Administration

  25. Reorganizing a Table DBMS_REDEFINITION steps: • Check the table – is it eligible • Create interim table with changes you want done • Start redefinition process • Finish redefinition process Each step (except #2) is a call to DBMS_REDEFINITION package Oracle9i Database Administrator: Implementation and Administration

  26. Making Other Table Changes Syntax of the ALTER TABLE command: ALTER TABLE <schema>.<tablename> RENAME TO <newname> LOGGING|NOLOGGING MONITORING|NOMONITORING ENABLE|DISABLE ROW MOVEMENT CACHE|NOCACHE Oracle9i Database Administrator: Implementation and Administration

  27. Making Other Table Changes ALTER TABLE components: • RENAME TO <newname> • LOGGING / NOLOGGING • MONITORING / NOMONITORING • ENABLE / DISABLE ROW MOVEMENT • CACHE / NOCACHE Oracle9i Database Administrator: Implementation and Administration

  28. Making Other Table Changes Example: Modify monitoring and cache: ALTER TABLE EMPLOYEE MONITORING CACHE; Oracle9i Database Administrator: Implementation and Administration

  29. Dropping, Adding, or Modifying a Column in a Table • Syntax for ALTER TABLE command: ALTER TABLE <schema>.<tablename> RENAME COLUMN <oldcolname> TO <newcolname> ADD (<colname> <datatype>, ... ) MODIFY (<colname> <datatype>, ... ) DROP (<colname>, <colname>,...)|COLUMN <colname> CASCADE CONSTRAINTS SET UNUSED (<colname>,<colname>,...)|COLUMN <colname> CASCADE CONSTRAINTS DROP UNUSED COLUMNS Note: Each of these clauses must be used alone in a single ALTER TABLE command. Oracle9i Database Administrator: Implementation and Administration

  30. Dropping, Adding, or Modifying a Column in a Table Examples: • Rename a column: ALTER TABLE CH08SURGERY RENAME COLUMN PATIENT_FISRT_NAME TO PATIENT_FIRST_NAME; • Add a column: ALTER TABLE CH08SURGERY ADD (OUTCOME VARCHAR2(40), OPERATING_ROOM_NO CHAR(4)); • Change length of column: ALTER TABLE CH08SURGERY MODIFY (DOCTOR_NAME VARCHAR2(20)); Oracle9i Database Administrator: Implementation and Administration

  31. Truncating and Dropping a Table TRUNCATE is fast: • No redo log entries • No undo records • Cannot rollback • Syntax: TRUNCATE TABLE <schema>.<tablename> DROP STORAGE|REUSE STORAGE Oracle9i Database Administrator: Implementation and Administration

  32. Truncating and Dropping a Table DROP command: • Removes data and structure • Must drop constraints that use the dropped table • Example: DROP TABLE COPCAR CASCADE CONSTRAINTS; Oracle9i Database Administrator: Implementation and Administration

  33. Querying Table-Related Data Dictionary Views Oracle9i Database Administrator: Implementation and Administration

  34. Querying Table-Related Data Dictionary Views Oracle9i Database Administrator: Implementation and Administration

  35. Querying Table-Related Data Dictionary Views Example: • Look at statistics gathered by monitoring tables: SELECT TABLE_NAME, TABLESPACE_NAME, MONITORING, BLOCKS, EMPTY_BLOCKS FROM USER_TABLES; Oracle9i Database Administrator: Implementation and Administration

  36. Chapter Summary • LOB data types are either internal LOBS or external LOBS • New features in the DBMS_LOB package simplify loading LOB data • Internal LOB values larger than 4000 bytes are stored out of line in a LOB data segment • Oracle9i works with LOBs by reading and writing one chunk at a time • LOB data segments can also be used to store varray data Oracle9i Database Administrator: Implementation and Administration

  37. Chapter Summary • Index-organized tables require a primary key and store data in order • Optionally split the column data into the main segment and an overflow segment • The ANALYZE command gathers statistics • The DBMS_STATS package also gathers statistics • Change a table’s storage parameters using the ALTER TABLE command Oracle9i Database Administrator: Implementation and Administration

  38. Chapter Summary • DBMS_REDEFINITION restructures a table while keeping it online • ALTER TABLE can do these tasks: • Move table to different tablespace • Release unused space • Rename the table • Modify columns (add, change, drop) • TRUNCATE removes rows permanently Oracle9i Database Administrator: Implementation and Administration

  39. Chapter Summary • TRUNCATE can release unused space or keep the space • DROP TABLE removes data and structure • CASCADE CONSTRAINTS if the table being dropped is connected by constraints to other tables Oracle9i Database Administrator: Implementation and Administration

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