Managing Automatic Storage Management Disk Groups

Purpose

This tutorial illustrates how to create a disk group with Enterprise Manager Database Control, and how Automatic Storage Management (ASM) rebalances disks when disk volumes are added to or removed from disk groups.

Time to Complete

Approximately 20 minutes

Topics

This tutorial covers the following topics:

	Overview
	Scenario
	Prerequisites
	Viewing a Disk Group with Enterprise Manager
	Adding Disks
	Removing a Disk
	Cleanup
	Summary

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Overview

This example illustrates how Automatic Storage Management manages the data stored on the disks available to it at the time. Striping is performed on the allocated disks. When a disk is removed, rebalancing is automatically performed, and the data is redistributed evenly across the remaining disks. When a disk is added, a proportional subset of data is evenly reallocated from the legacy disks to the newly added one.

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Scenario

A major part of the database performance equation is disk striping. This often requires many disks in production, and usually entails a lot of administration on the part of the DBA or the system administrator. Making disks available and then unavailable are common activities associated with that administration, and thus, having the Oracle instance react favorably to those changes is a desirable goal. In this scenario, a disk is taken away, and later made available to Oracle again, showing how ASM reacts by redistributing the data to take advantage of a disk's presence or accommodate its absence. This is done while the Oracle database, including the data that is being redistributed, is online and available for use as normal.

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Prerequisites

Before starting this tutorial, you should:

1.	Perform the Installing Oracle Database 10g on Windows tutorial.
2.	Perform the Configuring Automatic Storage Management tutorial.

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Viewing a Disk Group with Enterprise Manager

To view disk groups in an existing ASM instance, perform the following steps:

1.	Open your browser and enter the following URL (Replace <hostname> with your own host name or IP address): http://<hostname>:1158/em Enter sys as User Name, oracle as Password, SYSDBA in the Connect As field, and click Login.
2.	The Database home page appears with the ASM link in the General section. Click the ASM link.
3.	The Automatic Storage Management home page appears. Click the Administration tab.
4.	The first time you log in, enter sys as Username, oracle as Password, Connect As SYSDBA, select Save as Preferred Credentials, and click Login on the Automatic Storage Managment Login page.
5.	Click the link for the DGROUP1 disk group.
6.	View the disks in the disk group. Note that the data is evenly spread across the two available disks.

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Adding a Disk

To add a disk to a disk group in an ASM instance, perform the following steps:

1.	Return to the Enterprise Manager Console, and click Add in the Member Disks region of the Disk Group page..
2.	Select All Disks from the Select Member Disks drop-down list. The first time, you are using a newly stamped disk, its Header Status is PROVISIONED. If the disk has been previously dropped from a diskgroup and is now reused, its Header Status is FORMER.
3.	On the Add Disks page, select Rebalance Power 10, select also disk with the \\.\ORCLDISKDATA2 Path, enter DGROUP1_0002 as ASM Disk Name and click OK.
4.	View the newly added disk on the Disk Group page. Then click Refresh in your web browser window. You may be able to see the rebalancing progress, if you click Refresh repeatedly.

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Removing a Disk

To remove a disk from a disk group in an ASM instance, perform the following steps:

1.	On the Disk Group page, used in the last step of the previous topic, in the Member Disks region, select the disk DGROUP1_0002 and click Remove.
2.	Click Yes to confirm.
3.	When returned to the Disk Group page, click the Performance tab.
4.	Set the Refresh rate (see the top right of the page) to 30 seconds and observe how the graphs change after refreshing. Your graphs may be different from the ones displayed in the screenshot. Then click Home.
5.	On the Disk Group home page,.note that the DGROUP1_0002 disk has been removed.

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Cleanup

Drop the TBS1 tablespace and the DGROUP1 disk group (coming from tasks in the previous tutorial).

1.	Open a terminal window and execute the following command: SET ORACLE_SID=ORCL
2.	To start a SQL*Plus session for the ORCL isntance, enter: sqlplus sys/oracle as sysdba
3.	From your SQLPlus session, execute the following commands: drop tablespace tbs1 including contents and datafiles;* exit
4.	To switch to the +ASM instance, execute the following command: SET ORACLE_SID=+ASM
5.	To start a SQL*Plus session for the +ASM instance, enter: sqlplus sys/oracle as sysdba
6.	From your SQLPlus session, execute the following commands: drop diskgroup DRGOUP1 including contents;* exit
7.	Close all open tutorial windows.

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Summary

In this tutorial, you learned how to:

	View a disk group
	Remove and add a disk

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