# Overview The purpose of a 'dirty bit' is to track if the data in the cache was modified or not. If it has not been modified, there is no need to rewrite it to the database. If the dirty bit is on, there was a modification to the data in the database, which must be [[persisted]]. # Key Considerations # Pros - Necessary to keep track of data in a [[Write-back Cache]] - Reduces the total number of writes going against a database, thus improving performance # Cons - Adds complexity to a system # Use Cases # Related Topics