AUTOMATIC STORAGE MANAGEMENT (ASM)

Q: What does ASM provide? A: ASM provides a vertical integration of the file system and the volume manager that is specifically built for Oracle database files. Q: What are its key features and benefits? A: Stripes files rather than logical volumes Online disk reconfiguration and dynamic rebalancing Adjustable rebalancing speed Provides redundancy on a file basis Supports only Oracle database files Custer-aware Automatically installed Q: Does ASM have a data dictionary? A: ASM instance does not have a data dictionary and it is restricted to few SQL commands and Dynamic Performance view. Q: How do you create a disk group by using ASM? A: The following are examples of creating and deleting disk groups. Creating a disk group: SQL> CREATE DISKGROUP dgora1 NORMAL REDUNDANCY FAILGROUP controller1 DISK ‘/dev/rdsk/c0t0d0s2’ NAME mydisk SIZE 200G FORCE, ‘/dev/rdsk/c0t1d0s2’, ‘/dev/rdsk/c0t2d0s2’ FAILGROUP controller2 DISK ‘/dev/rdsk/c1t0d0s2’, ‘/dev/rdsk/c1t1d0s2’, ‘/dev/rdsk/c1t2d0s2’; Q: How do you delete a disk group by using ASM? A: Dropping a diskgroup: SQL> DROP DISKGROUP dgora1 INCLUDING CONTENTS; Q: How do you add a disk to an existing disk group? A: The following are examples of how to add disks to an existing disk group. SQL> ALTER DISKGROUP dgora1 ADD FAILGROUP controller1 ‘/dev/rdsk/c0t3d0s2’ NAME a5; Q: How do you remove a disk to an existing disk group? A: To remove a disk: SQL> ALTER DISKGROUP dgora1 DROP DISK a5; Q: Can you undo the removed disk? How? A: Yes. To undo the removed disk do the following SQL statement. This only works if the status of drop is pending or the drop function was not completed yet. SQL> ALTER DISKGROUP dgora1 UNDROP DISKS; Q: How do you display a list of your diskgroups? A: To display a list of diskgroups. SQL> SELECT name FROM v$asm_diskgroup; Q: How do you display a list of associated ASM disks? A: To display a list of associated ASM disks. SQL> COL name FORMAT a20 SQL> COL failgroup FORMAT a20 SQL> SELECT name, failgroup, bytes_read, bytes_written FROM v$asm_disk / Q: How do you display a list of associated ASM files? A: To display a list of associated ASM files. SQL> SELECT group_number, file_number, bytes, type, striped FROM v$asm_file / Q: How do you create a tablespace that uses an ASM disk group? A: To create a tablespace that is stored in the ASM disk group dgora1. SQL> CREATE TABLESPACE mytablespace2 DATAFILE ‘+dgora1’ SIZE 100m / Q: How do you add one addition disk to your system? A: Do the following. SQL> HOST dd if=/dev/zero of=/u02/oradata/school/diska abs=1024k count=200 SQL> SELECT name, failgroup, bytes_read, bytes_written FROM v$asm_disk / SQL> ALTER DISKGROUP dgora1 ADD DISK ‘/u02/oradata/school/diska’ / Execute the following query until you get ‘no rows selected.’ SQL> SELECT operation, est_minutes FROM v$asm_operation / Again, display a list of associated ASM disks. SQL> SELECT name, failgroup, bytes_read, bytes_written FROM v$asm_disk / Now, you should see one more disk was added to disk group