Oracle ASM interview Questions for the experienced- Part 1

 Here’s a list of Oracle ASM (Automatic Storage Management) interview questions designed for experienced candidates. These questions cover a range of advanced topics and scenarios, testing not only technical knowledge but also practical experience with Oracle ASM in real-world environments.

1. What is Oracle ASM, and how does it work?

• Expected Answer: Oracle ASM is a feature in Oracle Database that provides a simple and efficient storage management solution by managing disk groups, volumes, and files. It uses a volume manager and file system to manage data files, redo logs, control files, and backups. ASM abstracts the underlying storage hardware, allowing database administrators to focus on database management rather than disk management.

2. Explain the architecture of Oracle ASM.

• Expected Answer: Oracle ASM consists of the following components:
  • ASM Instance: An instance that provides the interface to ASM storage. It manages ASM disks and disk groups.
  • ASM Disk Group: A collection of disks managed by ASM. Disk groups store database files, control files, and archived logs.
  • ASM Disk: Physical disks or Logical Volume Manager (LVM) devices that are part of an ASM disk group.
  • ASM Metadata: Data stored in the control files of the ASM instance that tracks information about disk groups, file locations, and other configurations.

3. What is the difference between ASM and traditional file systems?

• Expected Answer: Oracle ASM is specifically designed for Oracle databases, providing optimized storage management. Unlike traditional file systems, ASM handles the distribution of data across multiple disks (striping), offers redundancy (mirroring or RAID), and automatically manages storage with minimal administrative effort. Traditional file systems require manual management for partitioning, file storage, and recovery, while ASM abstracts these tasks for database administrators.

4. What are the advantages of using Oracle ASM?

• Expected Answer: The key benefits of Oracle ASM include:
  • Simplified storage management.
  • Automatic file striping across multiple disks for performance.
  • Redundancy options like mirroring to ensure high availability.
  • Scalable storage architecture.
  • Integrated with Oracle database, simplifying backup, recovery, and performance management.
  • No need for third-party volume managers or file systems.
  • High performance for Oracle workloads.

5. How does Oracle ASM provide redundancy?

• Expected Answer: Oracle ASM provides redundancy through two primary methods:
  • Mirroring: Data is duplicated across multiple disks (normal redundancy or high redundancy).
  • RAID-like configurations: ASM uses a technique similar to RAID for striping and mirroring data across multiple disks.
  • Redundancy can be configured at the disk group level to ensure that if one disk fails, data remains accessible from another mirrored disk.

6. What are the different types of redundancy available in ASM?

• Expected Answer: ASM offers three levels of redundancy:
  • Normal Redundancy: Each file in the disk group is mirrored (2-way redundancy). Each file has two copies of the data (primary and mirror).
  • High Redundancy: Each file is mirrored three times (3-way redundancy). It provides higher availability, suitable for critical systems.
  • External Redundancy: No mirroring in ASM. This relies on external RAID devices or hardware to handle redundancy. Useful when external hardware redundancy is already in place.

7. What is the purpose of the ASM Disk Group?

• Expected Answer: A disk group is a collection of disks managed by ASM that stores Oracle database files such as data files, redo logs, and control files. Disk groups provide flexibility in storage management, allowing multiple disks to be treated as a single logical unit for the database. Disk groups can be configured for different levels of redundancy and performance.

8. How can you add a disk to an ASM Disk Group?

• Expected Answer: You can add a disk to an ASM disk group using the following steps:
  1. Ensure the disk is available and properly configured.
  2. Use the ALTER DISKGROUP SQL command to add the disk:

     
     ALTER DISKGROUP <diskgroup_name> ADD DISK '<disk_path>';
     

  3. You can also use asmcmd or Oracle Enterprise Manager (OEM) to add disks to the disk group.

9. How do you check the status of ASM disks and disk groups?

• Expected Answer: You can check the status using the following commands:
  • To check the status of ASM disks:

    
    SELECT * FROM V$ASM_DISK;
    

  • To check the status of disk groups:

    
    SELECT * FROM V$ASM_DISKGROUP;
    

  • Using asmcmd:

    
    asmcmd lsdg
    asmcmd lsdisk