Write Ahead Log
A Write-Ahead Log (WAL) is a durability technique in which a database records every change to a sequential log file before applying that change to its main data structures, ensuring changes can be recovered after a crash.
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Glossary Terms(2)
Write-Ahead Log
A Write-Ahead Log (WAL) is a durability technique in which a database records every change to a sequential log file before applying that change to its main dat…
B+ Tree Index
A B+ Tree index is a balanced, sorted tree data structure used by most relational databases to enable fast lookups, range scans, and ordered traversal of index…
Interview Questions(8)
What is Point-in-Time Recovery (PITR)?
Point-in-time recovery restores a database to its exact state at a specific past moment by combining a full backup with the replay of transaction logs up to th…
What is a Write-Ahead Log (WAL) and Why Do Databases Use One?
A write-ahead log (WAL) is a durability mechanism where the database records every change as a sequential log entry on stable storage before it modifies the ac…
How Does the Write-Ahead Log Enable Crash Recovery?
The write-ahead log enables crash recovery because, on restart, the database replays log records to redo committed changes that never made it to data pages, th…
What is Checkpointing in a Database and Why is it Needed?
Checkpointing is the process of periodically flushing all dirty (modified but unwritten) data pages from memory to disk and recording a marker in the write-ahe…
Redo Log vs Undo Log: What is the Difference?
A redo log records the new value produced by a change so committed effects can be reapplied after a crash, while an undo log records the old value that existed…
What is Transaction Log Shipping and How is it Used?
Transaction log shipping is a high-availability technique where the write-ahead or transaction log records generated on a primary database are continuously cop…
What is a Write-Ahead Log (WAL) and Why Do Systems Use It?
A write-ahead log is an append-only file that records every change durably before it is applied to the actual data structures on disk, so a crash can never los…
How Does a Write-Ahead Log Relate to an LSM-Tree?
A write-ahead log provides crash durability for a single write, while an LSM-tree is the broader storage engine architecture that uses that WAL alongside an in…