Category: oracle database

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.

 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

Click Here for More Details on ASM rebalancing

• 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.

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.

 Oracle Database 21c, the latest release from Oracle, introduces a wide array of new features and enhancements aimed at improving performance, security, automation, and cloud integration. As an Oracle DBA, staying on top of these new capabilities is crucial for optimizing database environments and supporting business requirements. Here are some of the key features in Oracle Database 21c that every DBA should know:

1. AutoML (Automated Machine Learning)

• What It Is: Oracle Database 21c introduces AutoML capabilities, allowing DBAs and developers to build machine learning models directly within the database without needing deep expertise in data science.
• Why It Matters: Machine learning integration directly within the database simplifies data analysis, predictive modeling, and decision-making, all without moving data outside of the database.
• Key Benefits:
  • Automated model training and evaluation.
  • Simplifies complex machine learning tasks like classification, regression, and clustering.
  • No need for separate data pipelines or tools.

2. Blockchain Tables

• What It Is: Oracle 21c introduces the concept of blockchain tables, where each row in a table is cryptographically secured, enabling tamper-proof data storage. These tables are ideal for use cases that require immutability and auditability, like financial transactions or supply chain tracking.
• Why It Matters: Blockchain tables can help ensure data integrity, enhance security, and provide an audit trail that guarantees the history of each transaction is immutable.
• Key Benefits:
  • Ensures immutability of data, making it ideal for audit-heavy use cases.
  • Integrates blockchain technology natively in the database.
  • Simplifies regulatory compliance by maintaining an incorruptible record of data changes.

3. JSON Enhancements

• What It Is: Oracle Database 21c brings enhanced support for JSON data types, with improved indexing, searching, and manipulation of JSON data. This includes support for “JSONPath,” which allows for more advanced querying of JSON documents.
• Why It Matters: JSON continues to grow in popularity as a format for semi-structured data, especially with modern web applications and RESTful APIs. The enhancements in 21c make working with JSON data more efficient and flexible.
• Key Benefits:
  • Full support for JSONPath queries (similar to XPath in XML).
  • Improved performance for JSON-based operations.
  • New indexing options that make querying JSON data faster and more efficient.

4. In-Memory Enhancements

• What It Is: Oracle Database 21c enhances the In-Memory column store feature, which allows for faster query performance by storing frequently accessed data in memory. The new enhancements allow for better control and more flexibility in how data is stored and retrieved in-memory.
• Why It Matters: In-memory computing continues to be one of the most powerful tools for speeding up database workloads, especially for analytic queries and real-time processing.
• Key Benefits:
  • Improved performance for analytics and real-time applications.
  • Enhanced control over memory usage and in-memory data management.
  • Support for Hybrid In-Memory where both OLTP and OLAP workloads can coexist in-memory.

5. Auto DDL (Data Definition Language) Management

• What It Is: Auto DDL automatically detects changes to the underlying database schema, such as the addition of new tables or columns, and propagates these changes to dependent objects. This feature is particularly useful when managing large, complex environments with many schema objects.
• Why It Matters: Reduces the need for manual intervention when making schema changes, simplifying database management and improving overall efficiency.
• Key Benefits:
  • Automatically handles schema changes without manual DDL updates.
  • Reduces human error and administrative overhead.
  • Helps DBAs manage schema changes in large, complex systems.

6. Multicloud and Hybrid Cloud Support

• What It Is: Oracle 21c enhances its integration with multicloud and hybrid cloud environments, providing more seamless cloud-to-cloud and on-premises-to-cloud management for databases. This includes improved data replication and migration tools.
• Why It Matters: As businesses increasingly adopt multicloud strategies, the ability to seamlessly manage Oracle databases across multiple cloud providers is critical for maintaining flexibility and optimizing cost.
• Key Benefits:
  • Easier management and migration between Oracle Cloud, on-premises, and other cloud providers.
  • Improved cross-cloud data replication for high availability.
  • Support for hybrid cloud architectures, making it easier to run Oracle databases across different environments.

7. Sharding Enhancements

• What It Is: Sharding enables horizontal partitioning of large databases to improve scalability and performance. Oracle 21c introduces enhancements to the sharding capabilities, including the ability to automatically rebalance shards and improve query performance.
• Why It Matters: Sharding is a critical feature for large-scale applications requiring high availability and scalability. These improvements make sharding easier to manage and more efficient.
• Key Benefits:
  • Automated rebalancing of data across shards for improved performance and load balancing.
  • Enhanced support for multi-tenant applications.
  • Simplified sharding administration, making it easier to scale large Oracle databases.

8. Improved Database Security (Including Data Redaction and Advanced Auditing)

• What It Is: Oracle Database 21c enhances security features with capabilities such as dynamic data redaction, which automatically masks sensitive data from unauthorized users, and improved auditing for more granular control over database activity.
• Why It Matters: As data privacy regulations become stricter (e.g., GDPR), securing sensitive data and ensuring compliance is critical for DBAs.
• Key Benefits:
  • Improved data redaction for masking sensitive data in real-time.
  • Enhanced auditing for better tracking of database activity.
  • Integration with Oracle Key Vault for more robust encryption management.

9. Automatic Indexing

• What It Is: Oracle 21c introduces an automatic indexing feature that allows the database to automatically create, manage, and drop indexes based on workloads. This removes the manual effort involved in index management and improves database performance.
• Why It Matters: Index management is often time-consuming, and poor indexing can severely affect performance. Automatic indexing allows DBAs to focus on other tasks while optimizing query performance.
• Key Benefits:
  • Automatic creation and tuning of indexes based on query workloads.
  • Reduces the need for manual intervention in index management.
  • Improves query performance and reduces overhead for DBAs.

10. SQL Macros

• What It Is: SQL Macros allow users to create reusable SQL code snippets that can be inserted into other SQL queries. These macros are similar to functions but can be used across different SQL statements.
• Why It Matters: SQL Macros can greatly improve productivity by enabling code reuse, simplifying maintenance, and reducing errors in complex queries.
• Key Benefits:
  • Encourages code reuse, reducing duplication and errors.
  • Simplifies complex queries by modularizing logic.
  • Improves performance and efficiency for DBAs and developers.

11. Hybrid Columnar Compression (HCC) for More Data Types

• What It Is: Oracle 21c extends Hybrid Columnar Compression (HCC) to more data types, allowing greater compression and storage optimization for a wider range of data, particularly for archival data.
• Why It Matters: With large datasets being common, efficient data compression is essential for reducing storage costs and improving performance in large-scale Oracle databases.
• Key Benefits:
  • Supports compression for more data types (e.g., LOBs, JSON).
  • Reduces storage footprint and improves query performance.
  • Ideal for large-scale OLTP and OLAP environments.

Oracle Database 21c introduces several cutting-edge features designed to help DBAs optimize performance, improve security, enhance scalability, and leverage modern technologies such as machine learning and blockchain. Mastering these new features will help DBAs stay ahead in a rapidly evolving IT landscape, whether managing on-premise databases, hybrid cloud architectures, or fully cloud-based environments.

In Oracle 19c, you can create a restore point to mark a specific point in time in the database to which you can later restore the database if needed. A restore point is typically used in conjunction with Flashback technology, which allows you to perform operations such as flashback database, flashback table, or flashback restore.

There are two types of restore points in Oracle 19c:

1. Normal Restore Point: A regular restore point that allows you to restore to that point in time.
2. Guaranteed Restore Point (GRP): This type of restore point guarantees that the database can be flashed back to this point, even if the archived logs required for recovery are no longer available.

Steps to Create a Restore Point in Oracle 19c

1. Creating a Normal Restore Point

To create a normal restore point, you can use the CREATE RESTORE POINT command.

CREATE RESTORE POINT restore_point_name;

For example:

CREATE RESTORE POINT my_restore_point;

This creates a restore point with the name my_restore_point. You can use this restore point later to perform flashback operations.

2. Creating a Guaranteed Restore Point (GRP)

A guaranteed restore point ensures that the database can be flashed back to this point even if the archive logs are lost. To create a GRP, use the GUARANTEE FLASHBACK DATABASE option.

CREATE RESTORE POINT restore_point_name GUARANTEE FLASHBACK DATABASE;

For example:

CREATE RESTORE POINT my_guaranteed_restore_point GUARANTEE FLASHBACK DATABASE;

This ensures that all necessary archived logs and undo data are retained to allow a flashback operation to this point.

3. Checking the List of Restore Points

To view a list of existing restore points, you can query the V$RESTORE_POINT view:

SELECT restore_point_name, guarantee_flashback, scn, time 
FROM v$restore_point;

4. Dropping a Restore Point

If you no longer need a restore point, you can drop it using the DROP RESTORE POINT command:

DROP RESTORE POINT restore_point_name;

For example:

DROP RESTORE POINT my_restore_point;

If the restore point is a Guaranteed Restore Point (GRP), Oracle will automatically remove the guarantee when you drop it.

5. Using a Restore Point for Flashback Operations

Once a restore point is created, you can use it to perform flashback operations such as FLASHBACK DATABASE or FLASHBACK TABLE.

For example, to flashback the entire database to a specific restore point:

FLASHBACK DATABASE TO RESTORE POINT my_restore_point;

Or, to flashback a specific table:

FLASHBACK TABLE my_table TO RESTORE POINT my_restore_point;

Note:

• Flashback Retention: For guaranteed restore points, make sure that Flashback Retention is appropriately set. If the required undo data is flushed before it is retained, the flashback operation might fail.
• Archivelog Mode: Ensure the database is in archivelog mode to take full advantage of flashback and restore point functionality.