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Dirty buffers in a database system refer to the modified data pages that have been modified in memory but not yet written back to the datafiles on disk. The process of writing dirty buffers to the datafiles is typically managed by a component known as the "write or checkpoint process."

When a buffer in memory becomes dirty due to modifications, the database system schedules a write operation to flush the dirty buffer back to its corresponding datafile on disk. This process ensures that the changes made in memory are durably persisted on disk for data integrity and consistency.

The write process can occur in different ways, depending on the database system's implementation and configuration. Some common approaches include:

1. Write-through: In this approach, every modification to a buffer is immediately written back to the corresponding datafile on disk. This ensures that all changes are persisted to disk at the cost of potential performance overhead.

2. Write-back or delayed write: Here, the dirty buffers are written back to the datafiles in batches or periodically rather than immediately after each modification. The database system manages a cache or buffer pool to hold the modified pages temporarily. The write-back process is triggered by factors such as the availability of free I/O resources, a certain threshold of dirty buffers, or a regular checkpoint operation.

3. Checkpoint: A checkpoint is a coordinated event where all dirty buffers up to a specific point in the transaction log are flushed to the datafiles. Checkpoints are periodically performed or triggered by specific conditions, such as system recovery, database backup, or reaching a certain threshold of dirty buffers.

During the write or checkpoint process, the dirty buffers are typically synchronized with the datafiles using disk I/O operations. The database system ensures that the changes are properly logged and persisted to maintain data consistency and durability.

It's important to note that the specific mechanisms and optimizations for writing dirty buffers to datafiles may vary across different database systems, configurations, and caching strategies.