PostgreSQL to Oracle: 2 Easy Steps

PostgreSQL is an Object-Relational Database Management System that focuses on SQL compliance and extensibility. This Open-Source Relational Database supports both JSON & SQL querying and serves as the primary data source for numerous mobile, web, geospatial, and analytics applications. Oracle has established itself as one of the largest vendors of RDBMS (Relational Database Management System) in the IT market since its inception. The query language that can be used to access data in Oracle’s relational databases is SQL.

This article talks about the steps you can follow to establish a connection from PostgreSQL to Oracle seamlessly. It also gives a brief introduction to PostgreSQL and Oracle before diving into the steps involved in setting up the connection.

What is PostgreSQL?

PostgreSQL is widely known for its Open-Source platform that supports all features of RDBMS. It also provides an array of features on top of RDBMS features like indexes, stored procedures, views, triggers, and atomicity features to name a few.

PostgreSQL runs on various major platforms like Windows, Linux, macOS, and UNIX to name a few. Concurrency is managed by PostgreSQL through Multi-Version Concurrency Control (MVCC). MVCC provides each transaction a “Database Snapshot” that allows changes to be made without impacting other transactions. This ensures the maintenance of ACID principles while doing away with the need to read locks.

Key Features of PostgreSQL

• Customizable: PostgreSQL can be customized by developing plugins to make the Database Management System fit your requirements. PostgreSQL also allows you to incorporate custom functions that are made with other programming languages like Java, C, C++, etc.
• Long History: PostgreSQL has been around for more than 30 years, having been initially released in 1988.
• Frequent Updates: The most recent PostgreSQL update was Version 13.1 on 12 November 2020.  
• MVCC Features: PostgreSQL happens to be the first Database Management System to implement Multi-Version Concurrency Control (MVCC) features.
• A Supportive Community: A dedicated community is always at your disposal. Private, third-party support services are available as well. The community updates the PostgreSQL platform via the PostgreSQL Global Development Group.
• Open-Source: This is an Object-Relational Database Management System(ORDBMS). This allows PostgreSQL to provide Object-Oriented and Relational Database functionality. PostgreSQL is a free and Open-Source ORDBMS.
• Users: PostgreSQL users include Apple, Cisco, Etsy, Facebook, Instagram, Red Hat, Skype, Spotify, and Yahoo to name a few.

What is Oracle?

Oracle offers a multi-model Database Management System popularly leveraged for Data Warehousing, Online Transaction Processing, and mixed database workloads. Oracle database runs on various major platforms like Linux, UNIX, Windows, and macOS. The Oracle database was the first database designed for Enterprise Grid Computing, which is the most cost-effective and flexible way to manage information and applications.

Enterprise Grid Computing develops large pools of industry-standard servers and modular storage. This type of architecture allows a new system to be swiftly provisioned from the pool of components. Since capacity can be easily relocated or added from the resource pool as needed, peak workloads are not required. It differs from the other types of computing through provisioning and virtualization.

Grid Computing aims to solve a few common problems faced by Enterprise IT by producing more resilient and lower-cost operating systems. This style of architecture allows Oracle to deliver a comprehensive database at a lower cost with greater flexibility and a higher quality of service. Oracle delivers on-the-grid computing functionality to focus on providing its users with centralized management, robust security infrastructure, universal access, and powerful development tools.

Key Features of Oracle

Here a some of the key features responsible for the immense popularity of Oracle.

• Cross-Platform Integration: Oracle supports and works on all operating systems (OS), including Windows, macOS, Linux, and others.
• Compliant with ACID Attributes: Oracle DB offers ACID (Atomicity, Consistency, Isolation, and Durability) properties to ensure the Database’s integrity during transaction processing.
• Simple Communication: Communication between applications on different platforms is simple. Oracle’s native networking stack allows you to seamlessly interface your database with applications on a variety of platforms. For example, you can simply link and interact with a Unix-based application with your Oracle database (running on Windows).
• Backup and Recovery: Oracle’s backup and recovery capabilities allow it to retrieve data from any accident or technical failure. Oracle’s RAC architecture ensures that all data and processes are backed up.
• Analytics Solutions: You can use Oracle Advanced Analytics and OLAP (Oracle Analytic Processing) to quickly do analytical computations on business data.

Understanding PostgreSQL to Oracle Migration Steps

Here are the steps involved in moving data from PostgreSQL to Oracle:

• PostgreSQL to Oracle Migration: PostgreSQL Export to CSV
• PostgreSQL to Oracle Migration: Export CSV Data to Oracle

PostgreSQL to Oracle Migration: PostgreSQL Export to CSV

• You can export data from a PostgreSQL table to a CSV file by using the COPY statement. For instance, if you want to export the data of the ‘persons’ table to a CSV file called persons_db.csv within the C:tmp folder, you can leverage the following statement:

COPY persons TO 'C:tmppersons_db.csv' DELIMITER ',' CSV HEADER;

• PostgreSQL will export all the data from all columns of the ‘persons’ table into the persons_db.csv file.
• In a couple of cases, you might want to export data from just a few columns of a table to a CSV file. To execute this, you need to specify the column names together with the table name followed by the COPY keyword. For instance, the following statement will export data from the last_name, first_name, and email columns of the ‘persons’ table to person_partial_db.csv.

COPY persons(first_name,last_name,email)
TO 'C:tmppersons_partial_db.csv' DELIMITER ',' CSV HEADER;

• If you don’t want to export the header that contains the column names for the table, you can simply remove the HEADER flag in the COPY statement. The following statement will only export the data from the email column of the ‘persons’ table to a CSV file.

COPY persons(email)
TO 'C:tmppersons_email_db.csv' DELIMITER ',' CSV;

• A point to note for the PostgreSQL to Oracle migration is that the CSV file name that you mention in the COPY command needs to be written directly to the server. This means that the CSV file needs to reside on the database server machine, as opposed to your local machine. The CSV file also needs to be writable by the user that the PostgreSQL server runs as. 

PostgreSQL to Oracle Migration: Export CSV Data to Oracle

• First, you need to decide the Oracle table you wish to use for the PostgreSQL to Oracle migration. If the PostgreSQL to Oracle migration is carried out on a new table, you can scroll to the Database menu, and click on Import Data. On the other hand, for an existing table, you can scroll to the Database Explorer, right-click a table, and choose Import Data on the shortcut menu for PostgreSQL to Oracle Migration.
• The Data Import wizard will open up with the predefined parameters: an Oracle connection, a table to import the data to, and a database.
• Next, in the Data Import Wizard, you can select a CSV import format, mention the location of the Source data, and click Next. Once you’re on the Data Import window, go to the Destination tab, mention the Oracle connection, choose the database and table to import the data to, and then click on Next.
• On the Data Import > Options tab, you can set the PostgreSQL to Oracle migration options for the file format you’ve chosen and then click on Next to execute the following:
  • You can select the line number where the table header is located. This will be highlighted in blue within the Preview section. If you don’t mention the header position, the imported columns will get default names- column1, column2, etc.
  • You can also set the number of lines to skip during the PostgreSQL to Oracle migration. These lines will be counted from the top.
  • You can even specify a column delimiter, the result of which can be viewed in the Preview section.

• Next, you need to scroll to the Data Import > Data Formats tab, wherein you can specify the data formats for the Source data, and then click on Next.
• You can then map the columns to the Target Table columns in the Data Import > Mapping tab.
• If you wish to cancel the mapping of all the columns, you can simply click on Clear Mappings on the toolbar. To restore the mapping of columns, you just need to click on Fill Mapping.

• If you are importing data to a new table, you can modify the Target column properties by double-clicking them in the top grid. Next, you need to select the Key check box for a column that contains a primary key and then click on Next.
• Next, you can pick an import mode for the data from the Data Import > Modes tab, and then click on Next.
• You can select one of the following PostgreSQL to Oracle migration options from the Data Import > Output tab, to manage the data import script, and then click on Next:
  • Open up the data import script in the internal editor
  • You can then save the data import script to a file
  • Finally, you can import data directly to the database
• You need to decide how to handle the errors during import on the Data Import > Errors Handling tab, and mention if you want to get a log file with details about the import session.
• To begin PostgreSQL to Oracle migration, you simply need to click on Import and look at the import progress. Finally, you can click on Finish to close the import wizard and complete the PostgreSQL to Oracle migration. 

Understanding the Architecture for Deploying a PostgreSQL Cluster on Oracle Cloud Infrastructure

This architecture shows a three-node deployment of a PostgreSQL Cluster on Oracle Cloud Infrastructure Compute instances. Here, the servers are configured in master and standby configuration and use streaming replication with file-based log shipping.

Recommendations

Your needs might differ from the architecture described above. You can leverage the following recommendations as a starting point for your configuration:

• VCN: When you generate a VCN, you can ascertain the number of CIDR blocks needed and the size of each block based on the number of resources that you’d like to attach to subnets within the VCN. You can also leverage CIDR blocks that are present in the standard private IP address space. Choose an address range that doesn’t overlap with your on-premise network, so that you can set up a connection between your on-premise network and the VCN if required. Once the VCN gets created, you can add, change and remove its CDR blocks. When you design your subnets, you need to keep your security requirements and functionality in mind. Keep all the compute instances within the same role or tier to the same subnet. 
• Compute Shapes: This architecture leverages an Oracle Linux 7.7 OS image along with a VM.Standard2.1 shape. You can pick a different shape if your application’s resource needs differ.

Considerations

Here are a few things you need to keep in mind when dealing with this cluster:

• Application Availability: Fault domains provide the best resilience within a solitary availability domain. This architecture uses a different approach to high availability: deploying Compute instances that can execute the same tasks across various fault domains. This design gets rid of a single point of failure by introducing redundancy. After the architecture is deployed, you can connect to the public IP address of the PostgreSQL node by leveraging SSH tools like Git Bash or PuTTY. You can use psql for DML and DDL operations on the PostgreSQL database. The PgAdmin tool can be used to perform administrative operations.
• Cost: Choose a Virtual Machine (VM) shape based on the cores, network bandwidth, and memory that you need for your database. You can begin with a one-core shape, and if you need more performance, network bandwidth, or memory for the database node, you can always modify the VM shape later. 
• Scalability: This architecture would deploy the PostgreSQL master node in one fault domain and the standby nodes in the other fault domains. You can scale the PostgreSQL cluster vertically by modifying the VM shape of every Compute Node. By leveraging a shape with a higher core count you can increase the memory allocated to the network bandwidth and the Compute instance.  

Conclusion

This article illustrates the steps you can follow to set up a connection from PostgreSQL to Oracle in a seamless fashion. For this method, you’ll first be moving your data from a PostgreSQL table to a CSV file, which will then be exported to Oracle. It also gives a brief introduction to Oracle and PostgreSQL before diving into the steps to establish the connection.

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