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Log Shipping

Definition

Log shipping is a process in which transaction log files of a database from a primary server are automatically backed up and delivered over a network to a standby server. The standby server restores the logs, keeping the two systems synchronized. This technique is often used for data replication and disaster recovery purposes.

Phonetic

The phonetic pronunciation of “Log Shipping” is: lɑg ʃɪpɪŋ.

Key Takeaways

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  1. Log Shipping is a high-availability and disaster recovery strategy where transaction logs are periodically backed up and restored on a standby server. This helps maintain an up-to-date secondary database for failover operations without user intervention.
  2. The major advantage of Log Shipping is minimal data loss. If the primary server fails, the latest transactions are available in the secondary server from the transaction logs. This minimizes data loss, optimizing data recovery.
  3. Despite the benefits, Log Shipping comes with some limitations. It does not automatically failover to the secondary server during primary server failure. It also doesn’t support server-level and cross-database transactions. The secondary databases are in a standby mode, so they are only readable when the transaction logs are not being restored.

“`The above points illustrate that Log Shipping provides a reliable method of backing up data and ensuring high-availability for database systems, although there are some caveats to take into consideration.

Importance

Log shipping is an important technology term because it relates to the process of automation in maintaining a backup of a database on a standby server. This is crucial as it enables the quick recovery of data and minimal disruption in case of any unforeseen circumstances or failures in the primary server. Moreover, log shipping also provides a disaster recovery solution and it can support multiple standby servers for one primary server. Therefore, log shipping is crucial for ensuring data security, business continuity, and seamless database functioning. It aids in maintaining the balance of the load and enhancing the overall efficiency of operations.

Explanation

Log shipping is a high-availability option that ensures business continuity by minimizing system downtime and providing disaster recovery solutions. The primary purpose of log shipping is to increase the availability of applications by maintaining a backup server, that can be made live if the primary server fails. It involves three main processes: backing up the transaction log at the primary (or production) server, transferring the log backup to one or more secondary servers, and restoring the log backup on the secondary server with a delay.This process provides a recovery mechanism and protects data from loss or damage. With log shipping, the secondary server can step in, in a read-only mode, to provide almost uninterrupted services if the primary server fails for reasons such as hardware failure, upgrades, or maintenance activities. Additionally, the data from the primary server is also replicated on the secondary server, enabling load balancing, as the secondary server can be used for querying and reporting purposes, thereby freeing up resources on the primary server. In essence, log shipping ensures business continuity, data availability, and effective resource utilization.

Examples

Log shipping is a process in which transaction log backups are taken from a primary database and then restored onto a standby database. This methodology ensures the availability and survivability of a database. The following are three real-world examples of log shipping:1. E-commerce Websites: Companies that manage e-commerce websites can require their databases to be always available so as not to disrupt transactions and reduce downtime. To achieve this, they may apply log shipping as it enables a backup server to step in immediately if the main server encounters problems.2. Banking Sector: In the world of banking, maintaining confidentiality, security, and availability of data is paramount. Log shipping provides the deployment of standby servers that allow banks to switch over quickly in the event of server failures, ensuring that their operations continue running smoothly.3. Supply Chain Management: Complex supply chain networks hold large amounts of crucial data. To prevent any data loss or downtime, companies may use log shipping to replicate transaction logs to a secondary server. This allows them to continue their operations in case the primary server fails.

Frequently Asked Questions(FAQ)

Q: What is log shipping?A: Log shipping is a high-availability and failover solution that involves automating the backup of transaction log files and other database files on a primary (production) server, and then restoring them on a standby server.Q: How does log shipping work?A: Log shipping works by periodically taking a backup of the transaction logs from the primary server and then restoring them on the standby server. The delay between backup and restore can be configured according to the business needs.Q: What are the benefits of log shipping?A: The benefits of log shipping include database recovery in case of system failures or disasters, load balancing for multiple databases, and maintenance of a backup server in the event the primary server goes down.Q: What are the requirements for log shipping?A: The requirements for log shipping typically include having two or more SQL Servers, a reliable network connection, sufficient space for storing backup files, and the SQL Server agent service must be running on all servers involved.Q: Are there certain databases that log shipping works best with?A: Log shipping is most effective with larger databases where complete backups would be time-consuming and impact performance. It allows for a standby database and seamless failover if needed.Q: Is log shipping suitable for real-time data replication?A: Log shipping isn’t suitable for real-time data replication due to the delay between taking backups from the original server and applying them to the secondary server. Q: What is the major difference between log shipping and database mirroring? A: The major difference between log shipping and database mirroring is that log shipping works on the database level, whereas database mirroring works on an instance level. Log shipping can deal with multiple databases while database mirroring can only work with a single database.Q: Does log shipping have any significant drawbacks?A: One potential drawback is the delay in copying logs from the primary server to the standby server, which means the standby server might not have the most recent transactions. Additionally, it can take some time to switch over to the standby server in the event of an issue.Q: What happens if the primary server fails during log shipping? A: If the primary server fails during log shipping, the most recent transactions may not have been copied to the standby server. As a result, some data could be lost. But overall, the standby server can be used with minimal data loss.

Related Tech Terms

  • Primary Server
  • Secondary Server
  • Transaction Log
  • Data Synchronization
  • Disaster Recovery

Sources for More Information

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