Contents
Why are database transactions useful?
Database transactions serve two main purposes. To conduct and bundle units of work that allow for accurate recovery of data in the case of system failures. To provide isolation between different programs which may attempt to access the data simultaneously.
What is transaction log and what is its function?
A transaction log is used to record the fact that a transaction is set to occur as well as the information needed by the database server to recover the data back to a consistent state in event of a sever failure while it is writing information to disk.
What is the importance of transaction?
Transaction logs are very important and fundamental to the proper operation of an Exchange server. The way Exchange eventually commits transactions to the database on an asynchronous basis means that it is entirely possible for users to read and write messages entirely in memory.
What are the properties of a transaction?
Transaction property
- Atomicity.
- Consistency.
- Isolation.
- Durability.
What are sufficient conditions to achieve the ACID properties?
ACID Properties A transaction is a very small unit of a program and it may contain several lowlevel tasks. A transaction in a database system must maintain Atomicity, Consistency, Isolation, and Durability − commonly known as ACID properties − in order to ensure accuracy, completeness, and data integrity.
Why do you need transaction log in SQL Server?
This transaction log is particular to a SQL Server database and there is, at least, one transaction log per SQL Server database. As explained on MSDN, the transaction log is a critical component of the database and, if there is a system failure, the transaction log might be required to bring your database back to a consistent state.
Why is it important to back up transaction log?
Since your transaction logs always keep a copy of all committed transactions on your database, you are guaranteed that all changes to your database are included when you back up your transaction log.
How to maintain a log of database changes?
Therefore, we need some way to indicate those tables that need their changes tracked. The two main challenges in creating an audit log of database changes is determining what mechanism will be used to log changes and how the history of changes will be persisted to the database.
How are transaction logs shrunk in SQL Server?
A log is shrunk when a DBCC SHRINKDATABASE statement is executed against the owning database, a DBCC SHRINKFILE is executed against the specific transaction log, or an autoshrink operation occurs if it is enabled on the database. When shrinking the log, it is first truncated to mark inactive records and then the inactive records are removed.