A dirty page is a term used in Microsoft SQL Server. A dirty page is a data page that has been modified in the buffer cache but still not transferred to disk.
When we execute any update query, the system updates the change in memory first and the corresponding data page has been marked as dirty.
SQL Server engine runs a process to write all such dirty pages back to disk.
Flushing is the process that writes all dirty pages back to disk. Several events can trigger the Flushing process.
A few are as below:
1. When the SQL Server engine needs to free up memory for other processes
2. When a checkpoint occurs
3. When a transaction commits
