Quick Answer
Every change is written to the transaction log before hitting data pages (Write-Ahead Logging). The log is sequential — fast to write. At CHECKPOINT, dirty pages flush to disk. On crash, SQL Server reads the log: redo commits that weren't in data files, undo uncommitted transactions. This sequence ensures full recoverability.
Answer
The transaction log is an append-only structure that records all modifications. SQL Server uses Write-Ahead Logging (WAL):
Log records are written to disk first
Data pages update later
This ensures atomicity and durability. Log truncation depends on checkpoints and active transactions.
S
SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
