Options for ASM disk Rebalancing

 

Additional Options for Rebalancing:

1. Check the Rebalance Status: You can monitor the progress of the rebalance process using the following query:

   
   SELECT * FROM V$ASM_OPERATION;
   

   This will show the current rebalancing status, including the percentage of completion and any other relevant details.

2. Cancel Rebalance: If you need to cancel a rebalance operation for any reason, you can use:

   
   ALTER DISKGROUP <diskgroup_name> CANCEL REBALANCE;
   

3. Set Rebalance Power (Speed): You can control the speed of the rebalance operation by adjusting the rebalance power. A higher power value results in a faster rebalance but uses more CPU resources. The default is 1 (low speed), and you can increase it up to 11 (fastest).

   Example:

   
   ALTER DISKGROUP <diskgroup_name> REBALANCE POWER 8;
   

   This would set the rebalance speed to level 8.

4. Force a Rebalance for Specific Disks: If you need to force the rebalance operation for specific disks in a disk group, you can use the FORCE option with the ALTER DISKGROUP command:

   
   ALTER DISKGROUP <diskgroup_name> REBALANCE FORCE;
   

Considerations:

• Rebalance Time: Depending on the amount of data and the number of disks involved, the rebalancing process can take some time. It's best to schedule it during off-peak hours to minimize the impact on performance.
• Diskgroup Operations: The rebalance operation redistributes the data across the disks in the disk group to ensure optimal usage of available storage.

Command to Rebalance ASM Disks:

 To rebalance ASM (Automatic Storage Management) disks in Oracle, you can use the ALTER DISKGROUP command in SQL*Plus or Oracle SQL Developer. Rebalancing typically occurs after disk additions, removals, or other changes to the ASM disk group.

ALTER DISKGROUP <diskgroup_name> REBALANCE;

Where <diskgroup_name> is the name of the ASM disk group that you want to rebalance.

Example:

ALTER DISKGROUP DATA REBALANCE;

This will trigger the rebalancing process for the DATA disk group.

To Monitor the progress of ASM rebalancing , query v$asm_operation table

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Oracle 19c Enhancements for Multitenant Architecture

 
Oracle 19c introduces several important updates to enhance multitenant functionality. Some of the most notable improvements include:

• Automatic PDB Relocation: Oracle 19c introduces automatic relocation of pluggable databases, which can help organizations balance workloads more effectively. This feature simplifies resource management and ensures that databases are running on the most optimal physical infrastructure.

• Plug-in and Plug-out for Pluggable Databases: In Oracle 19c, the process of plugging and unplugging PDBs is simplified. You can now migrate and transport PDBs between CDBs with minimal downtime and effort.

• PDB Snapshot Copies: Oracle 19c allows users to create snapshot copies of pluggable databases, which can be used for backup, testing, or staging. This feature enhances the ability to perform data recovery and testing without affecting the production environment.

• Enhanced Data Guard Support for Multitenant Environments: Oracle 19c improves support for multitenant environments in Data Guard. This feature ensures high availability by replicating the entire container database, including all its pluggable databases, to a standby system.

Use Cases for Oracle 19c Multitenant Architecture

1. Database Consolidation for Enterprises

   • Large enterprises often have hundreds or thousands of databases to manage. Oracle’s multitenant architecture allows businesses to consolidate databases from different departments, regions, or business units into fewer, more efficient instances. This reduces operational complexity and IT overhead while providing better resource utilization.

2. Cloud Deployments

   • Oracle multitenant architecture is particularly useful in cloud environments, where elasticity and scalability are key. It allows businesses to quickly spin up new databases for applications in the cloud while sharing resources across multiple databases. This ensures a cost-effective, flexible cloud strategy.

3. Testing and Development Environments

   • Developers and testers can use pluggable databases as isolated environments for testing applications, experimenting with different configurations, or staging new versions. By using PDB cloning, developers can quickly create copies of production databases for testing with minimal storage overhead.

4. SaaS Providers

   • SaaS providers can use Oracle’s multitenant architecture to host multiple customers’ databases in the same container database. Each customer gets a fully isolated, independent database (PDB), but the service provider benefits from resource sharing and centralized management.

Oracle Database 19c Multitenant Architecture

 

Oracle Database 19c introduces several key features designed to enhance performance, scalability, and management. Among these, Oracle’s multitenant architecture stands out as a game-changing innovation, offering organizations the ability to consolidate databases while ensuring high performance and simplified management. This blog post will explore how Oracle’s multitenant architecture in 19c can drive efficiency, reduce costs, and provide a scalable solution for modern database environments.

What is Oracle Multitenant Architecture?

Oracle Database’s multitenant architecture allows you to consolidate multiple databases (referred to as pluggable databases, or PDBs) into a single container database (CDB). This architecture offers distinct advantages over traditional database designs, including improved resource utilization, simplified management, and faster provisioning of databases.

In Oracle 19c, the multitenant architecture has been refined with several new enhancements, making it even more powerful for enterprises looking to streamline operations and cut costs. The key components of this architecture include:

• Container Database (CDB): The central database that houses one or more pluggable databases. It handles the overall database management functions.
• Pluggable Databases (PDBs): These are the individual databases that reside within the CDB. Each PDB is a self-contained, full-fledged database, but it shares common resources like memory and background processes with other PDBs within the same CDB.

Key Benefits of Oracle Multitenant Architecture in 19c

1. Resource Efficiency and Consolidation

   • One of the primary advantages of Oracle’s multitenant architecture is the ability to consolidate multiple databases on a single server. By sharing memory and background processes between pluggable databases, organizations can maximize hardware resources and reduce operational overhead. This consolidation not only improves hardware utilization but also simplifies administrative tasks such as backups and patching.

2. Simplified Database Management

   • Oracle 19c introduces enhanced management features for multitenant environments. Administrators can now manage multiple databases from a single control point (the CDB), making tasks like database provisioning, upgrades, and patching much easier. This reduces the complexity of managing large numbers of databases and helps in scaling systems more efficiently.
   • Features like automatic PDB relocation and Pluggable Database hot clone in 19c provide additional flexibility, enabling seamless database migrations and backup operations without significant downtime.

3. High Availability and Fault Isolation

   • With multitenant architecture, each PDB operates independently within the CDB. This means that if one PDB experiences an issue, it won’t affect other PDBs in the same CDB. This fault isolation enhances the overall availability and reliability of the database environment.
   • Additionally, Oracle Database 19c supports Data Guard and Active Data Guard for multitenant environments, offering robust disaster recovery capabilities for container databases and pluggable databases.

4. Cost Savings and Licensing Efficiency

   • Oracle’s multitenant architecture can lead to significant cost savings, especially in licensing. Traditional licensing for individual databases can be expensive, especially when you have a large number of databases to manage. With the multitenant model, Oracle provides a way to consolidate databases into fewer physical instances, thus reducing the total number of licenses required.
   • Oracle’s Oracle License Savings program further allows organizations to save on licensing costs when migrating to multitenant environments, as PDBs within a CDB share the same license count.

5. Faster Database Provisioning

   • With multitenant architecture in Oracle 19c, the time required to provision a new database is significantly reduced. PDBs can be created quickly and easily from a template, allowing for rapid deployment of new applications and services. This speed of provisioning is especially valuable for development, testing, and staging environments, where new databases are frequently needed.

6. Seamless Database Upgrades

   • Oracle Database 19c makes database upgrades easier in multitenant environments. The Pluggable Database upgrade feature allows organizations to upgrade PDBs independently of the CDB. This means that upgrading a database becomes a more modular and manageable process, reducing downtime and disruption.

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Expdp/Impdp FAQ's

1. What is the difference between expdp and impdp?

• Answer:
  • expdp (Data Pump Export): This utility is used to export database objects (tables, schemas, or entire databases) into a dump file. The export process can run in parallel and can be fine-tuned for performance.
  • impdp (Data Pump Import): This utility is used to import data from dump files created by expdp into a database. Like expdp, impdp also supports parallel execution and advanced filtering options.
  • Key Difference: While expdp is used for exporting data from Oracle databases, impdp is used for importing data back into Oracle databases.

2. What are the advantages of using Data Pump (expdp/impdp) over traditional exp/imp?

• Answer:
  • Performance: Data Pump utilities support parallel processing, which significantly speeds up both export and import operations.
  • Network Mode: Data Pump can export/import directly between databases over the network, bypassing the need for dump files.
  • Flexibility: More granular control over the export and import process (e.g., filtering tables, schemas, or partitions).
  • Incremental Exports: Data Pump supports incremental exports, allowing for only changes (new or modified data) to be exported since the last export.
  • Job Monitoring: Data Pump offers real-time monitoring and logging of operations.

3. Explain the concept of "PARALLEL" in Data Pump and how it improves performance.

• Answer:
  • The PARALLEL parameter allows multiple worker processes to run in parallel during an export or import operation. By dividing the task among multiple processes, the overall time for data transfer is reduced.
  • expdp and impdp can perform operations faster, especially with large datasets or highly partitioned tables, by utilizing multiple CPUs or cores.
  • The PARALLEL value specifies the number of parallel workers that should be launched to handle the job. The higher the number, the more parallelism you achieve (subject to system resources).

4. What is the role of the DIRECTORY parameter in expdp/impdp?

• Answer:
  • The DIRECTORY parameter specifies the directory object in the database where dump files will be written (for expdp) or read from (for impdp). This directory must be a valid directory object in Oracle, and it must be accessible to the Oracle Database Server. The directory path must be created and granted appropriate permissions to the Oracle user executing the job.
  • For example:

    
    CREATE DIRECTORY dump_dir AS '/path_to_directory';
    GRANT READ, WRITE ON DIRECTORY dump_dir TO <username>;
    

5. How can you perform a schema-level export using expdp?

• Answer: To export an entire schema, you can use the following command:

  
  expdp username/password DIRECTORY=dump_dir DUMPFILE=schema_export.dmp LOGFILE=schema_export.log SCHEMAS=schema_name
  

  • SCHEMAS: This specifies the schema(s) to export. You can list multiple schemas by separating them with commas.

6. What is the EXCLUDE parameter in Data Pump and how is it used?

• Answer:
  • The EXCLUDE parameter is used to exclude certain objects from the export or import operation. For example, you can exclude tables, indexes, or constraints from the export.
  • It is useful when you need to exclude specific objects to reduce the dump file size or to avoid exporting unnecessary objects.
  • Example of excluding tables:

    
    expdp username/password DIRECTORY=dump_dir DUMPFILE=export.dmp LOGFILE=export.log EXCLUDE=TABLE:"IN ('table1', 'table2')"
    

7. What is the INCLUDE parameter in Data Pump and how is it used?

• Answer:
  • The INCLUDE parameter allows you to include specific types of objects in an export or import job. This is the opposite of EXCLUDE.
  • You can use it to focus only on specific database objects, such as tables, schemas, or indexes.
  • Example of including only tables in the export:

    
    expdp username/password DIRECTORY=dump_dir DUMPFILE=export.dmp LOGFILE=export.log INCLUDE=TABLE:"='employees'"
    

8. What is the FLASHBACK_TIME parameter in expdp?

• Answer:
  • The FLASHBACK_TIME parameter allows you to perform an export as it appeared at a specific point in time. This is useful for exporting consistent data from a database as it was during a certain time, even if the data is being modified during the export process.
  • For example:

    
    expdp username/password DIRECTORY=dump_dir DUMPFILE=export.dmp LOGFILE=export.log FLASHBACK_TIME="TO_TIMESTAMP('2024-11-01 12:00:00', 'YYYY-MM-DD HH24:MI:SS')"
    

9. How do you perform a transportable tablespace export/import with expdp/impdp?

• Answer:
  • For transportable tablespaces, Data Pump can export and import entire tablespaces, reducing the time and complexity of moving large datasets between databases.
  • First, you need to set the TRANSPORTABLE parameter to ALWAYS or NEVER during the export:

    
    expdp username/password DIRECTORY=dump_dir DUMPFILE=export.dmp LOGFILE=export.log TRANSPORTABLE=ALWAYS TABLESPACES=ts_name
    

  • Then, use the impdp utility to import the tablespace into the target database:

    
    impdp username/password DIRECTORY=dump_dir DUMPFILE=export.dmp LOGFILE=import.log TRANSPORTABLE=ALWAYS
    

10. Explain the REMAP_SCHEMA parameter in impdp.

• Answer:
  • The REMAP_SCHEMA parameter allows you to map the schema from the source database to a different schema in the target database during an import operation. This is useful when the schema name on the source and target databases are different.
  • For example:

    
    impdp username/password DIRECTORY=dump_dir DUMPFILE=export.dmp LOGFILE=import.log REMAP_SCHEMA=old_schema:new_schema
    

11. What is the purpose of the ACCESS_METHOD parameter in expdp/impdp?

• Answer:
  • The ACCESS_METHOD parameter controls how the Data Pump job reads or writes the data. By default, Data Pump uses direct path when possible, but if the direct path is not available, it falls back to the conventional path.
  • The value for ACCESS_METHOD can be:
    • DIRECT_PATH: Uses direct path (faster) if possible.
    • CONVENTIONAL: Uses the conventional export/import method (slower).
  • Example:

    
    expdp username/password DIRECTORY=dump_dir DUMPFILE=export.dmp LOGFILE=export.log ACCESS_METHOD=DIRECT_PATH
    

12. How do you monitor the progress of an expdp or impdp job?

• Answer:
  • You can monitor the progress of an expdp or impdp job by querying the DBA_DATAPUMP_JOBS and DBA_DATAPUMP_SESSIONS views.
  • Example:

    
    SELECT * FROM DBA_DATAPUMP_JOBS WHERE JOB_NAME='YOUR_JOB_NAME';
    SELECT * FROM DBA_DATAPUMP_SESSIONS WHERE JOB_NAME='YOUR_JOB_NAME';
    

  • Additionally, the STATUS parameter in the LOGFILE will display progress during the job execution.

13. How can you restart a failed Data Pump job?

• Answer:
  • If a Data Pump job fails, you can restart the job from where it left off using the RESTART parameter.
  • Example:

    
    expdp username/password DIRECTORY=dump_dir DUMPFILE=export.dmp LOGFILE=export.log RESTART=Y