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INTRODUCTION TO ORACLE. Lynnwood Brown System Managers LLC Introduction to Oracle Automatic Storage Management (ASM). Copyright System Managers LLC 2008 all rights reserved. Introduction to ASM. File system preparation: On the filer: Create Aggregate from multiple disks

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introduction to oracle

INTRODUCTION TO ORACLE

Lynnwood Brown

System Managers LLC

Introduction to Oracle Automatic Storage Management (ASM)

Copyright System Managers LLC 2008 all rights reserved.

introduction to asm
Introduction to ASM

File system preparation:

On the filer:

  • Create Aggregate from multiple disks
  • Create volume(s) on the Aggregate
  • Create LUNs on the volumes (LUNs initiator groups maps WWPN/WWNN from the filer to the server.

On the Unix/Linux server:

  • Boot server to discover the new device
  • Run “mkfs” to create the file system
  • Create mount point
  • Mount device on the mount point

Copyright System Managers LLC 2008 all rights reserved.

introduction to asm1
Introduction to ASM

Automatic Storage Management (ASM)

  • Introduced in Oracle 10g, Automatic Storage Management (ASM) simplifies administration of Oracle related files by allowing the administrator to reference disk groups rather than individual disks and files, which are managed by ASM.
  • In an ASM environment the regular Unix/Linux file system is replaced by the ASM file system. The “mkfs” utility is NOT run.
  • ASM works with “raw” devices.
introduction to asm2
Introduction to ASM

ASM Instance Creation

  • Create instance initialization file ”init+ASM.ora” in the “/tmp” directory. Contents of the file: INSTANCE_TYPE=ASM
  • Connect to the ASM instance:
    • export ORACLE_SID=+ASM
    • sqlplus / as sysdba
  • Create instance “spfile”:

SQL> CREATE SPFILE FROM PFILE='/tmp/init+ASM.ora';

File created.

Copyright System Managers LLC 2008 all rights reserved.

introduction to asm3
Introduction to ASM

Start the ASM instance:

SQL> startup nomount

ASM instance started

Total System Global Area 125829120 bytes

Fixed Size 1301456 bytes

Variable Size 124527664 bytes

Database Buffers 0 bytes Redo Buffers 0 bytes

Copyright System Managers LLC 2008 all rights reserved.

introduction to asm4
Introduction to ASM

ASM Startup Options

  • FORCE - Performs a SHUTDOWN ABORT before restarting the ASM instance.
  • MOUNT - Starts the ASM instance and mounts the disk groups specified by the ASM_DISKGROUPS parameter.
  • NOMOUNT - Starts the ASM instance without mounting any disk groups.
  • OPEN - This is not a valid option for an ASM instance.

Copyright System Managers LLC 2008 all rights reserved.

introduction to asm5
Introduction to ASM

ASM Shutdown Options

  • NORMAL - The ASM instance waits for all connected ASM instances and SQL sessions to exit then shuts down.
  • IMMEDIATE - The ASM instance waits for any SQL transactions to complete then shuts down. It doesn't wait for sessions to exit.
  • TRANSACTIONAL - Same as IMMEDIATE.
  • ABORT - The ASM instance shuts down instantly.

Copyright System Managers LLC 2008 all rights reserved.

introduction to asm6
Introduction to ASM

ASMCMD

  • ASMCMD is a command-line utility that you can use to easily view and manipulate files and directories within Automatic Storage Management (ASM) disk groups. It can list the contents of disk groups, perform searches, create and remove directories and aliases, display space utilization
  • Accessing the ASMCMD CLI

Set ORACLE_HOME and ORACLE_SID to the ASM instance

Type asmcmd at the OS command prompt

ASMCMD >

Copyright System Managers LLC 2008 all rights reserved.

introduction to asm7
Introduction to ASM
  • Every file created in ASM gets a system-generated filename, otherwise known as a fully qualified filename. This is analogous to a complete path name in a local file system.
  • An example of a fully qualified filename is :

+dgroup2/sample/controlfile/Current.256.541956473

  • ASM generates filenames according to the following scheme:

+diskGroupName/databaseName/fileType/fileTypeTag.file.incarnation

  • In the previous fully qualified filename, dgroup2 is the disk group name, sample is the database name, controlfile is the file type, and so on.

Copyright System Managers LLC 2008 all rights reserved.

introduction to asm8
Introduction to ASM

Using ASMCMD commands example

  • ASMCMD [+] > cd +dgroup1
  • ASMCMD [+DGROUP1] > cd sample/datafile
  • ASMCMD [+DGROUP1/SAMPLE/DATAFILE] > ls EXAMPLE.269.555342243 SYSAUX.257.555341961 SYSTEM.256.555341961 UNDOTBS1.258.555341963 UNDOTBS1.272.557429239 USERS.259.555341963
  • ASMCMD [+DGROUP1/SAMPLE/DATAFILE] > rm undotbs1.272.557429239

Copyright System Managers LLC 2008 all rights reserved.

asmcmd commands
ASMCMD Commands

Copyright System Managers LLC 2008 all rights reserved.

introduction to asm9
Introduction to ASM

Creating ASM Disk Groups

Disk groups are created using the CREATE DISKGROUP statement. This statement allows you to specify the level of redundancy:

  • NORMAL REDUNDANCY - Two-way mirroring, requiring two failure groups.
  • HIGH REDUNDANCY - Three-way mirroring, requiring three failure groups.
  • EXTERNAL REDUNDANCY - No mirroring for disks that are already protected using hardware mirroring or RAID.
introduction to asm10
Introduction to ASM

Creating ASM Disk Groups

SQL > CREATE DISKGROUP disk_group_1 NORMAL REDUNDANCY FAILGROUP failure_group_1 DISK '/devices/diska1' NAME diska1, '/devices/diska2' NAME diska2, FAILGROUP failure_group_2 DISK '/devices/diskb1' NAME diskb1, '/devices/diskb2' NAME diskb2;

Disk Group Created

Dropping/deleting ASM Disk Groups

SQL > DROP DISKGROUP disk_group_1 INCLUDING CONTENTS;

Disk Group Dropped

Copyright System Managers LLC 2008 all rights reserved.

introduction to asm11
Introduction to ASM

Add disksto aDISKGROUP

SQL > ALTER DISKGROUP disk_group_1 ADD DISK '/devices/disk*3', '/devices/disk*4';

Note: The wildcard "*" can be used to reference disks so long as the resulting string does not match a disk already used by an existing disk group.

Drop disksfrom aDISKGROUP

SQL > ALTER DISKGROUP disk_group_1 DROP DISK diska2;

Copyright System Managers LLC 2008 all rights reserved.

introduction to asm12
Introduction to ASM

Disks can be resized using the RESIZE clause of the ALTER DISKGROUP statement. The statement can be used to resize individual disks, all disks in a failure group or all disks in the disk group. If the SIZE clause is omitted the disks are resized to the size of the disk returned by the OS.

Resize a specific disk.

SQL > ALTER DISKGROUP disk_group_1 RESIZE DISK diska1 SIZE 100G;

Resize all disks in a failure group.

SQL > ALTER DISKGROUP disk_group_1 RESIZE DISKS IN FAILGROUP failure_group_1 SIZE 100G;

Resize all disks in a disk group.

SQL > ALTER DISKGROUP disk_group_1 RESIZE ALL SIZE 100G;

introduction to asm13
Introduction to ASM

Creating a tablespace in an ASM environment:

SQL> CREATE TABLESPACE NEW_TS DATAFILE '+disk_group_1' SIZE 100M AUTOEXTEND ON;

Tablespace Created

Copyright System Managers LLC 2008 all rights reserved.

asm views
ASM Views

The ASM configuration can be viewed using the V$ASM_% views:

asm file names
ASM File Names

There are several ways to reference ASM file. Some forms are used during creation and some for referencing ASM files. The forms for file creation are incomplete, relying on ASM to create the fully qualified name, which can be retrieved from the supporting views. The forms of the ASM filenames are summarized below.

introduction to asm14
Introduction to ASM

ASM provides the following functionality:

  • Manages groups of disks, called disk groups.
  • Manages disk redundancy within a disk group.
  • Provides near-optimal I/O balancing without any manual tuning.
  • Enables management of database objects without specifying mount points and filenames.
  • Supports large files.

Copyright System Managers LLC 2008 all rights reserved.