Dale Roberts 1 Department of Computer and Information Science, School of Science, IUPUI Dale Roberts, Lecturer Computer Science, IUPUI Tablespaces

Dale Roberts 2 Tablespaces and terminology  Tablespace Tablespaces are a logical organization of space. Tablespaces owns the database’s datafiles. Database objects are stored within tablespaces.  Database: a logical collection of shared data stored in tablespaces.  File: A physical datafile belonging to a single tablespace.  Segment: A set of one or more extents that contains all the data for a specific structure within a tablespace. (TABLE, INDEX, CLUSTER, ROLLBACK, TEMP, etc.)  Extent: A set of contiguous data blocks with in a database that make up a segment.  Block: One or more physical file blocks allocated from an existing datafile.

Dale Roberts Oracle Tablespace Architecture datafile 1 datafile 2 datafile 3 datafile 4datafile 5 Database Blocks Extent 28K Extent 84K Segment 112K (Table, Index, etc.) TABLESPACE

Dale Roberts 4  Entity-Relationship Diagram showing: Database Tablespace Extents Segments Files Blocks Tablespace Data Model

Dale Roberts 5 Tablespace clause syntax Tablespace Clause: indicates Tablespace and other storage options for tables, indexes, constraints. Storage Clause: indicates how extents are managed, overrides the default storage parameters of tablespace. Syntax: CREATE TABLE tablename ( column_atype NOT NULL, column_btype,...) STORAGE ( INITIAL 100K NEXT 20K MINEXTENTS 1 MAXEXTENTS 99 PCTINCREASE 50 ) TABLESPACE USER_DATA PCTFREE 5 PCTUSED 30; CREATE TABLE tablename ( column_atype NOT NULL, column_btype,...) STORAGE ( INITIAL 100K NEXT 20K MINEXTENTS 1 MAXEXTENTS 99 PCTINCREASE 50 ) TABLESPACE USER_DATA PCTFREE 5 PCTUSED 30; The number of create table options is voluminous: NOLOGGING, NOPARALLEL, etc.

Dale Roberts 6 Tablespace and Segment Example SQL> select file_name, tablespace_name, bytes, blocks from dba_data_files FILE_NAME TABLESPACE_NAME BYTES BLOCKS /opt/oracle/u1/oradata/OS80/users01.dbf USERS /opt/oracle/u1/oradata/OS80/tools01.dbf TOOLS /opt/oracle/u1/oradata/OS80/temp01.dbf TEMP /opt/oracle/u1/oradata/OS80/rbs01.dbf RBS /opt/oracle/u1/oradata/OS80/system01.dbf SYSTEM /opt/oracle/u1/oradata/OS80/n311_t1.dbf N311TBS /opt/oracle/u1/oradata/OS80/csgrad_t1.dbf USERDATA_GRAD SQL> l 1 select tablespace_name, segment_name, segment_type, bytes, blocks, extents 2 from dba_segments 3* where owner = 'SCOTT' TABLESPACE_NAME SEGMENT_NA SEGMENT_TYPE BYTES BLOCKS EXTENTS SYSTEM BONUS TABLE SYSTEM SALGRADE TABLE SYSTEM WORKER TABLE SYSTEM TEMP_USERS TABLE SYSTEM LEDGER TABLE SYSTEM DEPT TABLE SYSTEM EMP TABLE SYSTEM PK_DEPT INDEX SYSTEM PK_EMP INDEX rows selected.

Dale Roberts 7 CREATE INDEX  Indexes: Contains values of data from a table and their location Pro: Used to speed data retrieval, also can enforce uniqueness. Con: Slows updates and deletes. When to use: if columns are typically used in where clause searches Primary keys and unique constraints create a unique index automatically. NULL values are not indexed.  Syntax: CREATE [BITMAP|UNIQUE] INDEX index ON table(COL1 [, COL2…] ) [REVERSE];  Other Oracle Index Features: Reverse indexes builds an index on the indexed column in reverse byte order thus increasing the dispersal of values. Bitmap indexes, new in 8 or 8i ?, associates a bitmap to values and only stores the bitmap in the index. Use with low cardinality values (e.g. T/F) Function based indexes, new in 8i. Normal indexes are not used if a function is used on the where clause column that you’re searching on.

Dale Roberts 8 CREATE CLUSTER  Clusters: Stores different tables physically together. The cluster key is the column that the data would normally be joined together with. Tables that share the same cluster are actually stored together and I/O is decreased when the two tables are joined.  Syntax Example: Create cluster BOOKandAUTHOR( col1 varchar2(1000)); Create table BOOKSHELF (title varchar2(100) primary key, … ) cluster BOOKandAUTHOR(title);

Dale Roberts 9 CREATE SEQUENCE  Sequences: Creates a unique sequentially valued number. Used during insert and update commands usually. Typically used to create a primary key. NextVal and CurrVal get the next/current value of the sequence.  Syntax: Create sequence myseq increment by 1 start with 1; Insert into CUSTOMER (id, name) values (myseq.nextval, ‘a’); Update OTHERTABLE set id = myseq.currval;

Dale Roberts 10 Acknowledgements Loney, Oracle Database 10g The Complete Reference