How to create ASM Disk group in Oracle 19C Database

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 In this post will see types of disk groups and how to create disk group, altering & delating disk group 

Types of Disk groups

 

Normal: Uses two-way mirroring. A normal redundancy disk group requires a minimum of two disk devices (or two failure groups).

 

External: Choosing not to use ASM mirroring of files

 

High: Uses three-way mirroring of Oracle ASM metadata and user data. A high redundancy disk group requires a minimum of three disk devices (or three failure groups). The effective disk space in a high redundancy disk group is one-third the sum of the disk space in all of its devices. A high redundancy disk group can tolerate two failures.

 

SYNTAX:-

 

CREATE DISKGROUP <DISKGROUP_NAME> REDUNDANCY DISK<'OSDISK_LOCATION'> NAME <FAILGROUP_NAME>;

 

What is mirroring & stripping?

 

Mirroring: Redundant copies of the data over multiple disks. 

 

Stripping: Spreading the data over multiple disks.


EXTERNAL REDUNDANCY  - No mirroring

 

Create the ASM DISK group

 

Find the disk group patch using below command

 

SQL> select group_number,name,failgroup,path from v$asm_disk;



SQL> CREATE DISKGROUP DATA_1 EXTERNAL REDUNDANCY DISK '/dev/oracleasm/disks/ASM_DISK5' NAME DISK_1;

 

Diskgroup created.

SQL>



Data_1 disk group created


Normal Redundancy:-

 

Uses two-way mirroring. A normal redundancy disk group requires a minimum of two disk devices (or two failure groups).

 

 

SQL> CREATE DISKGROUP DGROUPA NORMAL REDUNDANCY FAILGROUP CONTROLLER1 DISK '/dev/oracleasm/disks/ASM_DIS10' FAILGROUP CONTROLLER2 DISK '/dev/oracleasm/disks/ASM_DISK9';

 

Diskgroup created.


High Redundancy

 

Uses three-way mirroring of Oracle ASM metadata and user data. A high redundancy disk group requires a minimum of three disk devices (or three failure groups).

 

SQL> CREATE DISKGROUP DGROUPB HIGH REDUNDANCY FAILGROUP CONTROLLER1 DISK '/dev/oracleasm/disks/ASM_DISK8' FAILGROUP CONTROLLER2 DISK '/dev/oracleasm/disks/ASM_DISK6' FAILGROUP CONTROLLER3 DISK'/dev/oracleasm/disks/ASM_DISK4';

 

Diskgroup created.



Altering the DISK group:

 

Whenever we are adding the disk group based up on the redundancy we need to add the disks

 

SQL> ALTER DISKGROUP DGROUPA ADD DISK '/dev/oracleasm/disks/ASM_DISK11','/dev/oracleasm/disks/ASM_DISK7';

 

Diskgroup altered.



DROP Disk GROUP

 

DROP DISKGROUP <Diskgroup_name> INCLUDING CONTENTS;

Alter DISKGROPUP <DISKGROUP_NAME> DROP DISK <DISK_NAME>;

 

 

SQL> Alter diskgroup DGROUPA drop disk DGROUPA_0002;

 

Diskgroup altered.

 

SQL> Alter diskgroup DGROUPA drop disk DGROUPA_0003;

 

Diskgroup altered.

 

SQL> drop diskgroup DGROUPA;

 

Diskgroup dropped.

 

 

Reference:-

https://docs.oracle.com/en/database/oracle/oracle-database/19/ostmg/create-diskgroups.html#GUID-D8A4F1E1-D5F2-4372-8BF8-2A6CB9724930


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