What is Cold Backup and Hot Backup in Oracle?

In Oracle database management, backup strategies play a critical role in ensuring data availability, security, and recoverability. Two primary backup methods, hot and cold backups, are employed to safeguard database information. A hot backup is performed while the database is online and operational, allowing users to access and modify data concurrently.

A cold backup is conducted when the database is offline or in a shutdown state, ensuring consistency of the database at the backup initiation time. In this article, We will learn about the cold backup and hot backup in Oracle in detail.

A hot data backup in Oracle refers to the process of backing up the database while it is still online and operational also it allows users to access and modify data during the backup process. It is called an online backup. Hot backups use tools like Oracle Recovery Manager (RMAN) to take backups.

During the hot backup, Oracle continuously writes changes to the database redo logs. So those logs are used to fetch the database changes which are made during the backup process.

Examples: Hot backups are mainly used in the following domains.

• Finance: In banking and commodity markets, millions of transactions occur regularly every minute, so hot backup is preferred to keep the important financial information and continuously maintain workflow.
• Healthcare: Patient’s details need to be fetched at any time in the healthcare domain. so hot backup is suitable for this scenario.

The below image shows the hot backup working mechanism. Assume a banking application DB backup scenario. Here users send requests to servers regarding their account details and transactions. The server fetches the respective data from the DB while the DB backup is ongoing. So the application workflow remains uninterrupted and users can access their data without any disruption.

• Initially select a secure backup device such as a hard disk or network storage for storing backup files and check the DB access permissions before starting the backup.
  
• The next step is to select the relevant backup method. Use Oracle’s native tools like RMAN (Recovery Manager) for hot backups.
• Also, need to verify compatibility with the Oracle database version. Now start the hot-backup process using the selected method while the Oracle database remains online. So it is accessible to users.
• Take the backup of all essential database files, including data files, control files and redo log files.
• Finally, cross-check the backup files. Also, monitor the backup progress end-to-end to check the success rate and majorly implement the alerts to avoid issues or failures encountered during the backup process.

• Users can access the database throughout the backup process. So it ensures uninterrupted workflows.
• It supports fast data recovery while the database remains accessible. So downtime is less.

• It is more expensive to maintain because it requires high resources.
• The database may fail due to minor errors, making it less reliable in certain scenarios.

A cold data backup in Oracle refers to the process of backing up the database when it is offline or shut down. It’s also known as offline backup. During a cold backup, all database files, including data files, control files, and archived redo logs are copied while the database is not running. So it ensures that the backup represents a consistent snapshot of the database at the time the backup was initiated.

Examples: Cold backups are used in the following fields.

• Government and Military Systems: It’s suitable for sensitive government and military data backup. Cold backups provide security and protection from online threats.
• Scientific Research: Scientific research databases containing important experimental results and critical information. so cold backups are preferable.

The below image shows the cold backup working mechanism. Assume a Government application database backup scenario. Here users send requests to the servers regarding their account or important documents. However, the servers are in an inactive state due to the backup process and the database is shut down. So data cannot be retrieved by the users. In the cold backup, Proper initiation is given to the user via a notification or a message regarding the unavailability of services during the backup process.

• Before starting the cold backup, need to give proper initiation to the user via a notification about the unavailability of services.
• Initially shut down the Oracle database instance and prevent the ongoing transactions.
• Now copy database files such as data files, control files, and redo log files) to a backup device.
• The next step is to record the complete backup details such as the old DB version, date, time, and backup location for future reference.
• Once the backup is over. start the Oracle database instance and back to online.
• Finally, after backup cross-check the backup files. Also, monitor the backup progress and majorly implement the alerts to avoid any issues or failures.

• Cold backups increase data security because Cold backups work offline or in shutdown mode, so it preventing user access during the backup process. So it reduces unwanted database changes and deletions.
• It requires less budget. Cold backups require less infrastructure and resources compared to online backups.

• The major drawback of cold backup is downtime during the backup. So it’s not suitable for high transactional or active systems.
• Cold backups only provide access to data up to a specific point in time, So it limits flexibility in data recovery.

Overall, Hot and cold backups are essential strategies in Oracle database management, offering distinct benefits depending on the organization’s requirements. While hot backups provide continuous access to data, enabling uninterrupted workflows, cold backups offer a more secure and consistent snapshot of the database but require downtime. Understanding the differences between these backup methods allows organizations to choose the most appropriate approach based on their operational and security needs.