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How to Use Oracle’s Automatic Storage Management (ASM) for Efficient Storage

Introduction

Oracle’s Automatic Storage Management (ASM) is a powerful feature designed to simplify the management of database storage by providing an easy-to-use interface for database administrators. ASM integrates with Oracle databases to offer high performance, scalability, and reliability while reducing the complexity of managing storage systems. This tutorial is aimed at non-beginners who are already familiar with Oracle databases and storage concepts. We will explore the architecture, configuration, management, and optimization techniques for using ASM effectively.

1. Introduction to Oracle ASM

Oracle ASM provides a robust and flexible storage management solution for Oracle databases. It abstracts the physical storage into logical units, making storage management simpler and more efficient. ASM performs automated striping and mirroring, thus improving performance and reliability. With ASM, DBAs can manage database storage using a consistent and integrated approach, reducing the complexity and overhead typically associated with traditional storage management.

2. ASM Architecture and Components

Understanding the architecture and key components of ASM is crucial for effectively utilizing its capabilities. ASM consists of several core components, including the ASM instance, ASM disk groups, ASM disks, and ASM files.

ASM Instance

An ASM instance is a special type of Oracle instance that manages ASM disk groups. It is similar to a database instance but does not require a data dictionary. The ASM instance is responsible for managing metadata and performing tasks such as disk group creation, resizing, and rebalancing.

ASM Disk Groups

ASM disk groups are logical storage units that consist of multiple ASM disks. Disk groups provide the foundation for ASM storage management. Each disk group can be configured with different redundancy levels (normal, high, or external) to ensure data protection and availability.

ASM Disks

ASM disks are the physical storage devices that make up an ASM disk group. These can be physical disks, partitions, or logical volumes. ASM manages the disks, performing operations like striping and mirroring to optimize performance and reliability.

ASM Files

ASM files are the actual database files stored within ASM disk groups. These files include data files, control files, redo log files, and others. ASM files are managed by the ASM instance, which ensures efficient storage allocation and access.

3. Installing and Configuring ASM

Before using ASM, it must be properly installed and configured. This section covers the prerequisites, installation steps, and configuration of ASM instances and disk groups.

Prerequisites

Before installing ASM, ensure the following prerequisites are met:

  • Oracle Grid Infrastructure software is installed.
  • Sufficient storage devices (disks or partitions) are available for ASM disk groups.
  • Proper user permissions and groups are configured (usually the oracle user and dba group).

Installing ASM

ASM is installed as part of Oracle Grid Infrastructure. Follow these steps to install ASM:

  1. Download and extract Oracle Grid Infrastructure:
   unzip grid.zip -d /u01/app/gridCode language: Bash (bash)
  1. Run the Oracle Universal Installer (OUI):
   /u01/app/grid/gridSetup.shCode language: Bash (bash)
  1. Follow the installation wizard:
  • Select “Install and Configure Grid Infrastructure for a Standalone Server”.
  • Choose the appropriate Oracle Base and Software locations.
  • Configure the ASM disk groups by specifying the available storage devices.
  • Complete the installation and verify the ASM instance is running.

Creating ASM Instances

Once ASM is installed, create and configure ASM instances using the following steps:

  1. Create ASM initialization parameter file:
   vi /u01/app/oracle/product/19.0.0/dbhome_1/dbs/init+ASM.oraCode language: Bash (bash)

Add the following parameters:

   INSTANCE_TYPE=ASM
   ASM_POWER_LIMIT=11
   ASM_DISKSTRING='/dev/oracleasm/disks/*'Code language: plaintext (plaintext)
  1. Start the ASM instance:
   sqlplus / as sysasm
   startupCode language: SQL (Structured Query Language) (sql)
  1. Create ASM disk groups:
   CREATE DISKGROUP DATA EXTERNAL REDUNDANCY
   DISK '/dev/oracleasm/disks/DISK1',
        '/dev/oracleasm/disks/DISK2';Code language: SQL (Structured Query Language) (sql)

Creating ASM Disk Groups

ASM disk groups are created during the ASM instance configuration. Additional disk groups can be created as needed using SQL commands:

  1. Add a new disk group:
   CREATE DISKGROUP FRA NORMAL REDUNDANCY
   DISK '/dev/oracleasm/disks/DISK3',
        '/dev/oracleasm/disks/DISK4',
        '/dev/oracleasm/disks/DISK5';Code language: SQL (Structured Query Language) (sql)
  1. List existing disk groups:
   SELECT NAME, STATE, TYPE FROM V$ASM_DISKGROUP;Code language: SQL (Structured Query Language) (sql)

4. Managing ASM Disk Groups and Disks

Efficient management of ASM disk groups and disks is essential for maintaining optimal performance and reliability. This section covers adding and removing disks, rebalancing disk groups, and monitoring their status.

Adding and Removing Disks

ASM allows dynamic addition and removal of disks to disk groups, enabling flexible storage management.

  1. Add a disk to a disk group:
   ALTER DISKGROUP DATA ADD DISK '/dev/oracleasm/disks/DISK6';Code language: SQL (Structured Query Language) (sql)
  1. Drop a disk from a disk group:
   ALTER DISKGROUP DATA DROP DISK 'DISK6';Code language: SQL (Structured Query Language) (sql)
  1. Check the status of disks:
   SELECT NAME, STATE, MOUNT_STATUS FROM V$ASM_DISK;Code language: SQL (Structured Query Language) (sql)

Rebalancing Disk Groups

ASM automatically rebalances disk groups when disks are added or removed. The rebalancing operation redistributes data to maintain optimal performance.

  1. Manually initiate rebalancing:
   ALTER DISKGROUP DATA REBALANCE POWER 5;Code language: SQL (Structured Query Language) (sql)
  1. Monitor rebalancing status:
   SELECT GROUP_NUMBER, OPERATION, STATE, POWER, SOFAR, EST_WORK, EST_RATE, EST_MINUTES
   FROM V$ASM_OPERATION;Code language: SQL (Structured Query Language) (sql)

Monitoring ASM Disk Groups

Regular monitoring of ASM disk groups ensures they operate efficiently and helps identify potential issues early.

  1. View disk group usage:
   SELECT NAME, TOTAL_MB, FREE_MB, USABLE_FILE_MB, OFFLINE_DISKS
   FROM V$ASM_DISKGROUP;Code language: SQL (Structured Query Language) (sql)
  1. Check for alerts and warnings:
   SELECT MESSAGE, TIME
   FROM V$ALERT_HISTORY
   WHERE MODULE = 'ASM';Code language: SQL (Structured Query Language) (sql)

5. ASM File Management

Managing ASM files involves creating, managing, and accessing files stored within ASM disk groups. This section covers essential file management tasks and integrating ASM with Oracle databases.

Creating and Managing ASM Files

ASM files are created and managed using SQL commands or Oracle tools such as Oracle Enterprise Manager (OEM).

  1. Create a tablespace using ASM:
   CREATE TABLESPACE myts DATAFILE '+DATA' SIZE 100M;Code language: SQL (Structured Query Language) (sql)
  1. Move an existing file to ASM:
   ALTER DATABASE MOVE DATAFILE '/u01/app/oracle/oradata/mydb/system01.dbf' TO '+DATA';Code language: SQL (Structured Query Language) (sql)
  1. List ASM files:
   SELECT FILE_NUMBER, FILE_TYPE, TABLESPACE_NAME, BYTES
   FROM V$ASM_FILE;Code language: SQL (Structured Query Language) (sql)

Using ASM with Oracle Database

Integrating ASM with Oracle Database involves configuring the database to use ASM for storage.

  1. Set the DB_CREATE_FILE_DEST parameter:
   ALTER SYSTEM SET DB_CREATE_FILE_DEST = '+DATA';Code language: SQL (Structured Query Language) (sql)
  1. Create database objects using ASM:
   CREATE TABLE mytable (id NUMBER, name VARCHAR2(50))
   TABLESPACE myts;Code language: SQL (Structured Query Language) (sql)
  1. Manage ASM file access permissions:
   ALTER DISKGROUP DATA SET ATTRIBUTE 'access_control.enabled' = 'true';Code language: SQL (Structured Query Language) (sql)

ASM Templates

ASM templates define the default properties for ASM files, such as redundancy and striping.

  1. Create a custom ASM template:
   ALTER DISKGROUP DATA ADD TEMPLATE mytemplate ATTRIBUTES (REDUNDANCY HIGH, STRIPE_WIDTH 1M);Code language: SQL (Structured Query Language) (sql)
  1. Use a template when creating a tablespace:
   CREATE TABLESPACE myts DATAFILE '+DATA(mytemplate)' SIZE 100M;Code language: SQL (Structured Query Language) (sql)

6. Performance Tuning and Optimization

Optimizing ASM performance involves following best practices, tuning disk groups, and monitoring performance metrics.

ASM Best Practices

  1. Distribute I/O evenly across disks: Ensure disks in a disk group have similar performance characteristics.
  2. Use appropriate redundancy levels: Choose the right level of redundancy based on performance and availability requirements.
  3. Regularly monitor and maintain ASM: Use Oracle tools and scripts to monitor disk group usage and performance.

Tuning ASM Disk Groups

  1. Adjust rebalancing power: Set the rebalancing power to balance between performance and rebalancing speed.
   ALTER DISKGROUP DATA REBALANCE POWER 10;Code language: SQL (Structured Query Language) (sql)
  1. Optimize disk group configuration: Regularly review and adjust the configuration to ensure optimal performance.
   ALTER DISKGROUP DATA RESIZE ALL SIZE 200G;Code language: SQL (Structured Query Language) (sql)
  1. Use intelligent data placement: Leverage ASM’s intelligent data placement feature to optimize data location based on access patterns.

Monitoring and Troubleshooting Performance

  1. Use Oracle Enterprise Manager (OEM): OEM provides comprehensive tools for monitoring and managing ASM performance.
  2. Monitor performance metrics:
   SELECT GROUP_NUMBER, TOTAL_MB, FREE_MB, USABLE_FILE_MB, OFFLINE_DISKS
   FROM V$ASM_DISKGROUP;Code language: SQL (Structured Query Language) (sql)
  1. Analyze wait events:
   SELECT EVENT, TOTAL_WAITS, TIME_WAITED
   FROM V$SYSTEM_EVENT
   WHERE EVENT LIKE 'asm%';Code language: SQL (Structured Query Language) (sql)

7. ASM Backup and Recovery

Backing up and recovering ASM metadata and disk groups is crucial for ensuring data availability and integrity.

Backing Up ASM Metadata

  1. Use the ASMCMD utility:
   asmcmd md_backup /u01/app/oracle/backup/asm_metadata.bakCode language: Bash (bash)
  1. Schedule regular backups: Automate ASM metadata backups using cron jobs or Oracle Scheduler.

Recovering ASM Disk Groups

  1. Restore ASM metadata:
   asmcmd md_restore /u01/app/oracle/backup/asm_metadata.bakCode language: Bash (bash)
  1. Recover from disk failures: Replace failed disks and use the ASM recovery commands to restore data.
   ALTER DISKGROUP DATA MOUNT;Code language: SQL (Structured Query Language) (sql)

8. Advanced ASM Features

ASM offers several advanced features to enhance its capabilities and integration with other Oracle technologies.

ASM Flex and Flex Redundancy

ASM Flex provides flexible deployment options for ASM instances and disk groups, improving scalability and availability.

  1. Enable ASM Flex:
   ALTER SYSTEM SET asm_flex_enabled = TRUE;Code language: SQL (Structured Query Language) (sql)
  1. Configure Flex redundancy:
   CREATE DISKGROUP FLEXDATA FLEX REDUNDANCY DISK '/dev/oracleasm/disks/DISK1';Code language: SQL (Structured Query Language) (sql)

ASM Cluster File System (ACFS)

ACFS extends ASM capabilities to provide a scalable, high-performance file system.

  1. Create an ACFS file system:
   asmcmd mkfs -t acfs +DATA/vol1Code language: Bash (bash)
  1. Mount the ACFS file system:
   mount -t acfs /dev/asm/vol1-123 /mnt/acfsCode language: Bash (bash)

Integration with Oracle Cloud

ASM integrates seamlessly with Oracle Cloud, enabling hybrid and cloud-native deployments.

  1. Configure ASM for Oracle Cloud Infrastructure (OCI): Use Oracle Cloud tools and APIs to manage ASM storage in cloud environments.
  2. Leverage cloud-native features: Integrate ASM with Oracle Autonomous Database and other cloud services for enhanced performance and scalability.

9. Conclusion

Oracle ASM provides a comprehensive solution for managing database storage efficiently. By understanding its architecture, configuring and managing disk groups, optimizing performance, and leveraging advanced features, database administrators can ensure high performance, scalability, and reliability for their Oracle databases. This tutorial has covered the essential aspects of using ASM, providing a solid foundation for mastering this powerful storage management tool.

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