Month: November 2024

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.

Click Here for more details on Oracle Database 19c Multitenant Architecture

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

New features in Oracle Database 21c every DBA should know

 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.

Top Certifications required for Oracle Apps DBAS

 As Oracle Apps DBAs continue to evolve their skills in a rapidly changing IT landscape, certifications remain a key differentiator for career advancement. For 2024, focusing on certifications that validate expertise in both Oracle Applications and Database technologies, particularly in the cloud era, can enhance your career prospects. Below are the top certifications for Oracle Apps DBAs in 2024:

1. Oracle Certified Professional (OCP) – Oracle Database Administration

  • Overview: Oracle’s OCP certifications are one of the most sought-after credentials for database professionals. This certification validates your ability to manage Oracle databases, including installation, configuration, backup and recovery, performance tuning, and security.
  • Why It’s Important: With Oracle’s focus on the cloud, OCP remains an essential foundational certification for DBAs who manage traditional on-premise Oracle databases and hybrid environments.
  • Key Topics:
    • Backup and Recovery with RMAN
    • Performance Tuning and Optimization
    • Security Management
    • Troubleshooting Oracle Database
  • Recommended For: DBAs who manage on-premise Oracle Databases (Oracle 19c/21c) in either traditional or cloud-based environments.

2. Oracle Cloud Infrastructure (OCI) Architect Associate

  • Overview: With Oracle’s cloud-first strategy, understanding how to deploy and manage Oracle E-Business Suite (EBS) and databases on Oracle Cloud Infrastructure (OCI) is essential. This certification demonstrates proficiency in designing, deploying, and managing infrastructure using OCI services.
  • Why It’s Important: As Oracle Apps DBAs increasingly migrate to the cloud, this certification allows DBAs to handle cloud workloads, infrastructure automation, and security on OCI.
  • Key Topics:
    • Core OCI services (Compute, Storage, Networking, and Identity & Access Management)
    • Cost Management and Pricing for OCI
    • Security and Backup in OCI
    • Disaster Recovery and High Availability on OCI
  • Recommended For: DBAs working with Oracle Cloud-based applications and databases, particularly Oracle EBS or Oracle Autonomous Database.

3. Oracle E-Business Suite R12 Certified Implementation Specialist

  • Overview: This certification validates expertise in implementing, managing, and troubleshooting Oracle E-Business Suite (EBS) applications. It covers a wide range of functional and technical topics, including database administration, setup, configuration, and performance tuning of EBS.
  • Why It’s Important: Oracle EBS continues to be a core suite of applications for large enterprises, and a DBA with expertise in both EBS and database management is highly sought after.
  • Key Topics:
    • EBS architecture and database management
    • Application tuning and troubleshooting
    • EBS migration and upgrade
    • EBS backup, recovery, and security
  • Recommended For: DBAs working with Oracle EBS, particularly those managing large EBS implementations or migrations.

4. Oracle Autonomous Database on Shared Infrastructure (OCA)

  • Overview: Oracle Autonomous Database is a cloud-based solution that leverages machine learning to automate key database tasks such as tuning, patching, and scaling. This certification demonstrates proficiency in deploying, configuring, and managing Autonomous Databases.
  • Why It’s Important: As Oracle moves toward cloud-first solutions, understanding the inner workings of Autonomous Database is critical for DBAs managing cloud applications and services.
  • Key Topics:
    • Autonomous Database deployment and configuration
    • Database patching and upgrades in Autonomous DB
    • Automated tuning, performance management, and scaling
    • Managing security and backups in Autonomous Database
  • Recommended For: DBAs working with Oracle Autonomous Database and Oracle Cloud services.

5. Oracle Database 19c/21c Certified Expert

  • Overview: The Oracle Database 19c and 21c certifications provide an in-depth focus on the newest database versions, including features such as high availability, security, and machine learning capabilities. These certifications are ideal for DBAs managing both on-premise and cloud databases.
  • Why It’s Important: Oracle Database 19c is the long-term release supported by Oracle, and 21c introduces cutting-edge features. Mastery of these versions is essential for DBAs handling enterprise-grade databases.
  • Key Topics:
    • Advanced performance tuning
    • Partitioning and clustering
    • Backup, recovery, and high availability
    • Security management and user access control
  • Recommended For: DBAs managing Oracle Database 19c/21c environments, especially those handling large-scale enterprise applications.

6. Oracle Applications DBA: R12.2 Database Administration

  • Overview: This certification focuses on the administration of Oracle E-Business Suite (EBS) R12.2. It targets DBAs who manage Oracle EBS databases and ensures they are well-versed in database performance, tuning, patching, and backup/recovery.
  • Why It’s Important: Oracle E-Business Suite R12.2 remains one of the most widely used enterprise resource planning (ERP) systems. DBAs with this certification can demonstrate their ability to support EBS in both on-premise and cloud environments.
  • Key Topics:
    • Installing and configuring Oracle EBS R12.2
    • Managing Oracle EBS R12.2 patching and upgrades
    • Performance tuning and troubleshooting
    • Managing database backups and recovery strategies
  • Recommended For: DBAs specializing in the support and management of Oracle E-Business Suite (EBS) R12.2 environments.

expdp fails with UDE-31623: operation generated ORACLE error 31623

 


Issue:

expdp fails with error 


UDE-31623: operation generated ORACLE error 31623

expdp “/as sysdba” tables=EMP directory=DATA_PUMP_DIR dumpfile=emp.dmp logfile=emp.log

 
Export: Release 19.0.0.0.0 - Production on Fri Nov 22 04:15:27 2024
Version 19.24.0.0.0
 
Copyright (c) 1982, 2019, Oracle and/or its affiliates.  All rights reserved.
 
Connected to: Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
 
UDE-31623: operation generated ORACLE error 31623
ORA-31623: a job is not attached to this session via the specified handle
ORA-06512: at "SYS.DBMS_DATAPUMP", line 4747
ORA-06512: at "SYS.KUPV$FT_INT", line 2144
ORA-06512: at "SYS.DBMS_SYS_ERROR", line 79
ORA-06512: at "SYS.KUPV$FT_INT", line 2081
ORA-06512: at "SYS.DBMS_DATAPUMP", line 2263
ORA-06512: at "SYS.DBMS_DATAPUMP", line 4496
ORA-06512: at "SYS.DBMS_DATAPUMP", line 6127
ORA-06512: at line 1
 
Cause

ORA-4031 errors in alert log
ORA-04031: unable to allocate 56 bytes of shared memory ("streams pool","unknown object","streams pool","fixed allocation callback")





Solution





Check SGA parameters and increase as per requirement





In our case, 





SQL> show parameter sga_target value is less than sga_max_size.


Increased sga_target to fix the issue


NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
sga_max_size                         big integer 12G
sga_target                           big integer 10880M


SQL> alter system set sga_target=12G scope=both;

System altered.

How to create restore point in Oracle database 19c

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.

Oracle ASM Interview Questions for the experienced – Part 2

 Click Here for ASM Interview Questions – Part 1

10. What is ASM rebalance, and how does it work?

  • Expected Answer: ASM rebalance is the process of redistributing data across the disks in a disk group when there is a change in the disk group (e.g., adding or dropping a disk). The rebalance operation ensures that data is evenly spread across the available disks to optimize performance and storage. It occurs automatically when disk group changes are made and can be monitored with the v$asm_operation view.

11. How does ASM handle disk failure?

  • Expected Answer: When a disk fails in a redundant disk group (using mirroring), Oracle ASM automatically rebalances the data to the remaining healthy disks. If you are using external redundancy, you may need to rely on external RAID for recovery. ASM detects disk failures via periodic disk checks and logs the failure, making it easy for administrators to take action, such as adding a replacement disk.

12. How do you migrate data from one ASM disk group to another?

  • Expected Answer: To migrate data from one ASM disk group to another, you can:
    1. Use the ALTER DISKGROUP command to move data: 

      ALTER DISKGROUP <source_diskgroup> MOVE <file_name> TO <target_diskgroup>;
    2. Use DBMS_FILE_TRANSFER or other tools like RMAN for moving data files between disk groups.
    3. Alternatively, you can use Data Pump for migrating large datasets.

13. How would you recover from a disk failure in Oracle ASM?

  • Expected Answer: To recover from a disk failure in ASM:
    1. Identify the failed disk using V$ASM_DISK.
    2. Ensure that the disk group is still operational (in case of mirroring, data is still available on the other disks).
    3. Replace the failed disk physically.
    4. Add the new disk to the ASM disk group using ALTER DISKGROUP ADD DISK.
    5. Oracle ASM will automatically rebalance the data across the disks, ensuring data is mirrored correctly.

14. Explain the role of the ASM instance and the Oracle database instance in an ASM-enabled database.

  • Expected Answer: The ASM instance manages the physical storage (disk groups and disks) and provides the storage abstraction for the Oracle database. It operates independently from the Oracle database instance, which connects to the ASM instance for reading/writing data files, control files, and redo logs. The database instance communicates with the ASM instance via Oracle background processes (e.g., DBWR, LGWR).

15. What is the difference between ASM and RAID?

  • Expected Answer: ASM is a software-based storage management solution that operates within the Oracle Database ecosystem. While it provides features similar to RAID (redundancy, striping, etc.), it is tightly integrated with Oracle databases and handles file management and storage distribution automatically. RAID, on the other hand, is a hardware or software-based technology used for disk redundancy and performance at the hardware level, but it lacks the database-level integration that ASM offers.

16. Can you configure Oracle RAC (Real Application Clusters) with ASM?

  • Expected Answer: Yes, Oracle RAC can be configured with ASM for shared storage across multiple nodes. In RAC, multiple database instances run on different nodes, and ASM provides shared disk storage, which ensures that all instances have access to the same database files stored in ASM disk groups. ASM simplifies the storage configuration for RAC by handling disk management in a cluster environment.

17. What are the ASM parameters you can modify to tune performance?

  • Expected Answer: Some key ASM parameters for tuning performance include:
    • ASM_DISK_REPAIR_TIME: Defines the time allowed for disk repairs.
    • ASM_POWER_LIMIT: Controls the amount of CPU resources ASM can use during rebalancing.
    • ASM_DISKGROUP_REPAIR_TIME: Specifies the time allowed for repairing the disk group in case of a failure.

18. How do you monitor ASM performance?

  • Expected Answer: You can monitor ASM performance using the following methods:
    • V$ASM views: Use views like V$ASM_DISK, V$ASM_DISKGROUP, and V$ASM_OPERATION to track ASM performance and disk operations.
    • Oracle Enterprise Manager (OEM): OEM provides a graphical interface to monitor ASM performance, including disk group usage, rebalance status, and storage health.