This document discusses parallel processing in Oracle databases. It provides hints and commands for enabling and controlling parallel execution for SQL statements, DML, DDL and other operations like loading, recovery and replication. It also covers concepts like the structure of Oracle rowids and storage parameters for tables.

1. Anar Godjaev
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Parallel Server
Parallel Hints
Select /*+PRALLEL(<tb_name>, 8|DEFAULT)*/
/*+NOPARALLEL(<tb_name>)*/
/*+PARALLEL_INDEX(<tb_name>, <ind_name>,3,2)*/
/*+NOPARALLEL_INDEX*/
1- alter table <tb_name> parallel (degree 8)
2- select /*+PARALLEL(<tb_name>,<degree>) from <tb_name>
PARALLEL_ADAPTIVE_MULTI_USER
(user number is high: set up; degree level up: set down)
Parallel DML|DDL:
Alter session [enable|disable] parallel [dml|ddl];
İnsert /*+PARALLEL(emp_big,4,1)*/ into <table_name>
Parallel DDL:
Create table <tb_name> parallel (degree 8)
Create index <ind_name> on <tb_name> (<col_name>).... parallel (degree 8)
Parallel Loading:
Sqlldr direct=true parallel=true
Parallel Recovery:
Recover tablespace<tbs_name> parallel (degree [8|DEFAULT])
Parallel Replication:
DBMS_DEFER_SYS.SCHEDULE_PUSH
(
DESINATION -> ‘par1.world’,
INTERVAL -> ‘sysdate+1/24,
NEXT_DATE -> ‘sysdate+1/24’,
PARALLELISM -> 6
);
Alter session force parellel DDL parallel 5;
degree of parallelism ‐‐number of parallel execution servers
‐ A PARALLEL clause in a statement
‐ The PARALLEL clause that was used when the object was created or altered
‐ A parallel hint inserted into the statement

2. Anar Godjaev
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‐ A default determined by Oracle
Parallel execution can be tuned for you automatically by setting the initialization parameter;
PARALLEL_AUTOMATIC_TUNING = TRUE
Alter session ENABLE | DISABLE PARALLEL DDL | DML ;
Alter session force PARALLEL DDL | DML PARALLEL 5;
Alter system set parallel_max_servers = <degree of max parallism>;
***** *****
***** *****
Extended rowid needs 10 bytes of storage on disk, is displayed by 18 chars.
Data object number //table,index//32 bits
Relative file number //unique for each file //10bits
Block number //position of the block //22 bits
Row number //position of the row //16 bits
SQL>select department_id, row_id from hr.departments;
Create table hr.employees(Employee_id number(6),
First_name varchar2(20),
Last_name varchar2(25),
Hire_date date default sysdate) Storage(Initial 200k,
Next 200k,
Pctincrease 0,
Minextents 1,
Maxextents 5) Tablespacedata;
Create temprary table hr.employees_temp as select * from hr.employees;
Compute pctfree and pctused values
Pct used: [(Average row size – initial row size) * 100] / Average row size
Pct used: [100 – pct free – (average row size * 100)] / Available data space
SQL> Alter table hr.employeespctfree 30 pctused 50 storage(
Next 500k
Minextents 2
Maxextents 100);
Alter table hr.employees allocate extent (size 500k datafile ‘/disk3/data1.dbf’);
Alter table hr.employees move tablesapce data1;
Truncate table hr.employees;
Drop table hr.employees cascade constrains;

3. Anar Godjaev
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Alter table hr.employees drop column comments cascade constrains checkpoint1000;
Alter table hr.employees set unusued column comments cascade constrains;
Alter table hr.employees drop unusued columns checkpoint 1000;
Dba_tables
Dba_objects