With the rise of modern technologies, there has been an exponential surge in data generation. This influx of data necessitates the continuous availability of information from diverse locations. In essence, this entails the real-time replication of data to multiple accessible platforms. Capitalizing on these technological advancements, organizations now possess the capability to store and analyze data across varied repositories. Accomplishing this entails the need for efficient tools to seamlessly transfer data across different data stores, business intelligence applications, and data analytics platforms.

Oracle stands out as a prominent data platform extensively adopted for enterprise data storage. Renowned for its capacity to handle massive workloads and process millions of transactions, Oracle has become a favored database choice for numerous businesses. To share data residing within the Oracle database with other systems and databases, establishing a method to access Oracle-held data becomes indispensable.

To execute this process effectively, the use of an appropriate replication tool becomes paramount. This tool facilitates the easy duplication and transfer of data to alternative databases and data warehouses. Oracle replication emerges as a technique to enable the integration and accessibility of multiple databases, ensuring enhanced data performance and availability. Additionally, various other tools can also serve this purpose.

In this article, we will delve into the realm of Oracle replication, investigating methodologies that facilitate the replication of data to alternative databases.

What is Oracle

Whenever tech buzzwords like database software, cloud solutions, and enterprise software products are heard, Oracle is one of the computer technology corporations that comes to our minds. Oracle’s most successful product is Oracle Database, a relational database management system (RDBMS) widely used for managing and storing structured data. It is one of the most widely used and respected database systems in the industry. Oracle Database is designed to efficiently store, manage, and retrieve structured data while providing a range of advanced features for data security, scalability, availability, and query performance optimization.

Features of Oracle 

• Relational Model: Oracle Database follows the relational model that is storing the data in format of tables with rows and columns. It uses SQL (Structured Query Language) to read or write the data.
• Data Integrity: The Oracle Database enforces data integrity through various constraints, ensuring accuracy and reliability of stored data.
• Data Security: Oracle Database offers comprehensive security features such as user authentication, role-based access control, data encryption, and auditing to protect sensitive information.
• Scalability: The database can scale both vertically (adding more resources to a single server) and horizontally (adding more servers to a cluster) to accommodate increasing data volumes and user loads.
• Performance Optimization: The Oracle optimizer analyzes queries and generates efficient execution plans, leveraging indexing, caching, load balancing, decreasing CPU overhead and parallel processing for optimal performance.
• Advanced Analytics: It supports advanced analytics and data mining through features like analytical functions, advanced statistics, and machine learning integration.
• Development Tools: Oracle offers a range of tools for developing, testing, and managing database applications, including SQL Developer, PL/SQL, and Application Express (APEX).
• Cloud Integration: Oracle provides cloud-based database services, allowing organizations to migrate, deploy, and manage databases in the cloud.

What is database replication in oracle 

Database replication in Oracle refers to the process of creating and maintaining one or more copies of a database for various use cases in a way that the copies are in sync with the original one. Its purpose is to enable organizations to achieve various goals such as high availability, data recovery, data distribution, load balancing, reporting etc which will be discussed in the next section.

In Oracle database replication, changes made to the source database are captured and applied to one or many destination databases, ensuring that the data in the target databases remains in sync with the source. Oracle offers several replication methods to achieve this synchronization, each with its own benefit which we would deep dive into the article.

Importance of database replication in oracle 

Oracle database replication holds significant importance for multiple scenarios and additionally for solving critical problems of organizations across different use cases:

• Data Recovery: A replicated database ensures that a standby copy is readily available in case the primary database experiences a failure. This additional standby database can be used anytime to perform the operations, hence replacing the primary one, minimizing the outage damage and ensuring smooth business operations. Replicated databases can also act as live backups. In case data corruption occurs in the primary database, you can use the replicated copy to restore data without affecting any business operations. 
• Data Redundancy and Scalability: On replication of databases redundant copies of data are created, which can be used individually for various scenarios like read operations, reporting, and analytics. This helps in load balancing and reducing database overhead for the primary database from read-intensive queries and helps maintain acceptable performance for all types of query transactions. By distributing read and write operations across replicated databases, you can also achieve load balancing and improve the scalability and ensure that the primary database doesn’t become a bottleneck of any application. 
• Geographical Distribution of Databases: Storing replicated databases across multiple locations or data centers allows organizations to provide a more smooth and almost lag-free experience to the users or clients in different geographic regions. Geographical distribution of databases helps reduce latency for remote users.
• Data Analysis and Reporting: Replicated databases are extensively used by organizations to store data from multiple sources into a single destination for centralized reporting and analysis, providing a unified view of the data. A separate replicated database can be used for data analysis and reporting which would not affect the performance of the primary database. This is crucial for organizations that need to analyze historical data or generate complex reports and distribute OLAP vs OLTP databases. In some database replication methods like Oracle GoldenGate, real-time data synchronization is achieved, enabling consistent data across multiple databases for immediate and effective real-time analysis which would help in achieving accurate decision-making.
• Maintenance of Databases: Replicated databases are a fundamental component of a diversified and optimal business operations plan. It ensures that critical systems and data is readily available even during maintenance and unexpected events like outage, database connector issues etc. During unexpected events, system upgrades or maintenance, replicated databases ensure there is zero downtime. You can direct the users to a replicated database, allowing the primary database to be upgraded or fixed without affecting any business operations.
• Data Integration and Data Security: Replication can facilitate data migration between diversified areas like cloud databases, SaaS platforms etc, allowing smooth data transfers without affecting business operations. Replicated databases can also help in meeting regulatory requirements by maintaining redundant copies of sensitive data for audit and compliance purposes to ensure there are no data leaks or data breach and all the permissions are respected during data transfer between the different platforms.

Overall, Oracle database replication addresses the need for high availability for reporting and analysis, data redundancy, data recovery, data security, optimal performance, and flexibility in managing data across different scenarios, ensuring that critical data remains accessible, safe and usable for ensuring smooth operations of applications even in challenging circumstances.

What are the types of replication in oracle?

There are several types of Oracle database replication methods that allow you to make copies of data in different databases for various purposes. Each Oracle database replication method has its own advantages and use cases. Here are the main types of Oracle database replication methods:

Physical Standby Database (Data Guard):

Oracle Data Guard provides data recovery and high availability solutions by creating an exact duplicate, or standby, of the primary database. Changes from the primary database's are applied to the standby database, ensuring sync. In the event of a primary database failure, the standby database can be seamlessly switched over. It can be preferred for data recovery and planned maintenance use cases.

Logical Standby Database:

A logical standby database replicates data by applying SQL statements from the primary database. This method enables more flexibility in terms of applying DML and DDL changes, which can be useful for scenarios requiring data transformation or migrations. It is useful for reporting, data migration and data transformation cases.

Snapshot Replication:

Snapshot replication involves creating chunks of data making a batch from source data periodically and these batches can be transferred to the destination database. This method is ideal for scenarios where near-real-time replication is not required, since the data will be transferred periodically. Businesses who need to do periodic reporting, historical data analysis can benefit a lot from this type of replication.

Materialized View Replication:

Materialized views have the results of a predefined query and can be refreshed on-demand or based on changes in the source data. These views improve query performance and can serve as a form of data replication. This method is ideal for query performance optimization, data aggregation, and data distribution.

Oracle Streams:

Oracle Streams provides a flexible system for capturing and implementing changes at the database object level. It offers complete control over the changes that are captured and how they are applied to target databases. Customized data replication, data transformation, database synchronization are few of the use cases for this type of replication.

Oracle GoldenGate:

‍Oracle GoldenGate is a powerful solution for real-time data replication and integration across various environments. It enables regular movement of data between databases, regardless of their location or platform. Real-time data integration, data warehousing, and business problems are few of the use cases where this type of relocation could be ideal.

Each replication method brings its unique strengths, addressing different scenarios based on data sync requirements, availability goals, and the complexity of data transformations needed. The selection of a replication strategy should be chosen by keeping specific needs and objectives of the organization in mind.

Steps to setup oracle database replication
Oracle database replication involves using SQL and PL/SQL scripts to manage the replication process. Depending on the replication method you choose (logical, physical, snapshot, GoldenGate, etc.), the specific steps and scripts will vary. Below, are a high-level overview of how you might approach Oracle database replication using few commands:

Step 1: Choosing Oracle database replication method
Decide the Oracle replication method such as physical standby, logical standby, snapshot replication, or using Oracle GoldenGate that suits your requirements.

Step 2: Set up the destination database
Ensure the destination database is properly configured and ready to receive replicated data. This involves creating necessary tablespaces, users, and other structures.

Step 3: Configure database replication

Method 1: Logical Replication
Logical replication involves replicating data and applying changes at the SQL level. You'll typically use Oracle Streams or other custom scripts for this method.

Step 1: Replicating Data

• Create a capture process using the `DBMS_CAPTURE_ADM` package or equivalent SQL commands.
• Specify the source tables and changes you want to capture.
• Set up rules to filter and transform captured data if needed.

-- Enable force logging

ALTER DATABASE FORCE LOGGING;

-- Create a logical standby control file

ALTER DATABASE CREATE STANDBY CONTROLFILE AS 'path_to_control_file';

-- Enable supplemental logging

ALTER DATABASE ADD SUPPLEMENTAL LOG DATA;

-- Enable table-level supplemental logging

ALTER TABLE <table_name> ADD SUPPLEMENTAL LOG DATA (PRIMARY KEY);

Step 2: Apply Changes

• Create an apply process using the `DBMS_APPLY_ADM` package or equivalent SQL commands.
• Define the target tables and the rules for applying changes.
• Monitor the apply process to ensure changes are propagated correctly.

-- Configure the standby database

ALTER DATABASE SET STANDBY DATABASE TO '<primary_db_unique_name>';

-- Start managed recovery

ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;

Method 2: Physical Replication

Physical replication involves replicating database files at the storage level. Oracle Data Guard is a common tool for physical replication.

Step 1: Configure Data Guard

• Identify the primary database and setup a standby database.
• Enable archiving on the primary database to generate redo logs.
• Configure Data Guard to automatically apply redo logs to the standby database.

-- Enable archiving on the primary database

ALTER DATABASE ARCHIVELOG;

-- Create a standby redo log

ALTER DATABASE ADD STANDBY LOGFILE GROUP <group_number> ('path_to_log_file') SIZE <size>;

-- Configure log shipping

ALTER SYSTEM SET LOG_ARCHIVE_DEST_2='SERVICE=<standby_service> LGWR SYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE)';

Step 2: Monitor and Manage Data Guard

• Use SQL scripts or Data Guard commands to monitor the status of the replication.
• Failover to the standby database in case of primary database failure.

-- Create a standby control file

ALTER DATABASE CREATE STANDBY CONTROLFILE AS 'path_to_control_file';

-- Configure the standby database

ALTER DATABASE SET STANDBY DATABASE TO '<primary_db_unique_name>';

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-- Start managed recovery

ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;

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Method 3: Snapshot Replication

Snapshot replication involves periodically taking snapshots of the data and applying them to the target.

Step 1: Create Snapshots

• Write SQL scripts to create snapshots of the source tables.
• Schedule the snapshots to run at specified intervals.
  
  

-- Create a snapshot table

CREATE TABLE <snapshot_table> AS SELECT * FROM <source_table>;

-- Schedule snapshot creation

CREATE OR REPLACE PROCEDURE create_snapshot AS

BEGIN

   EXECUTE IMMEDIATE 'TRUNCATE TABLE <snapshot_table>';

   EXECUTE IMMEDIATE 'INSERT INTO <snapshot_table> SELECT * FROM <source_table>';

   COMMIT;

END;

/

Step 2: Apply Snapshots

• Write SQL scripts to apply the snapshots to the target database.
• Schedule the application process to run after snapshots are created.
  
  

-- Apply the snapshot to the target database

INSERT INTO <target_table> SELECT * FROM <snapshot_table>;

COMMIT;

Method 4: GoldenGate Replication

Oracle GoldenGate is a comprehensive data replication solution. It involves using its own set of scripts and configurations.

Step 1: Configure GoldenGate

• Set up GoldenGate source and target environments.
• Define extract processes to capture changes from the source.
• Define replicate processes to apply changes to the target.

Step 2: Monitor GoldenGate

• Monitor the status of extract and replicate processes using GoldenGate commands.
• Handle errors and conflicts as they arise.

In all cases, you'll need a good understanding of Oracle SQL, PL/SQL, and the specific replication method you're using. Oracle's documentation for each replication method provides detailed information on the necessary scripts, commands, and configurations. It's recommended to thoroughly review the documentation and understand all the technical aspects with respect to system environment and requirements to ensure a successful implementation.

Step 4: Maintaining and Monitoring
Whichever method you choose, you'll need to continuously monitor and manage the replication process. This involves using SQL queries and monitoring tools provided by Oracle or the chosen replication solution.

Step 5: Testing and validations

Ensuring that a replicated database can handle the operations in case of a primary database failure is a must. To test the database replication setup you can simulate failures and perform failovers on to the original database and ensure the replicated database is able to handle primary database failure.

Please note that these are simplified steps for oracle database replication which provide a high-level view of the process. The actual implementation can be more tedious and complex, especially for Oracle GoldenGate. Configuration steps vary based on the specific requirements and system environments. Always go through the detailed Oracle's official documentation and possibly involve experienced DBAs for setting up replication in a production environment or you can always opt for an low-code data replication solution like Fivetran.

Drawbacks of using oracle database replication

Oracle database replication is essential and has various offerings like data availability, redundancy, and scalability, yet there are some drawbacks of various replication methods.

• Physical standby replication through Data Guard provides data recovery but demands complex configurations and additional resources.
• Logical standby replication provides flexibility but the complexity of applying DML and DDL modifications might impact performance. 
• Snapshot replication's periodic updates and manual refreshes can hinder real-time data needs.
• while materialized view replication enhances query performance, it also introduces data latency.
• Oracle GoldenGate despite having so powerful capabilities brings complexity in configuration and licensing costs. 

Also, there is a drawback which anyone might occur while going for any of the method:

• While replicating the data in the destination database there might be a need to write custom scripts to transfer data accurately as the data could be changing at frequent intervals in the source database. Also, real-time Oracle Database replication might be tedious to carry out for less tech savvy teams.

Using Fivetran for oracle database replication

It's pretty much clear that carrying out the database replication is one of the hardcore engineering projects which anyone could think of by looking at the challenges involved. It requires a significant bandwidth and man hours to carry out such complex replication tasks. This is where you can leverage a near real-time low-code tool, Fivetran. There is no need for any coding because it can automate your replication task. You can also visit Connector Directory | Fivetran, to explore various other connectors supported by Fivetran.

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