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I answered on LinkedIn about how transaction log, redo log, and WAL are the same.
In practice MSSQL transaction log ~= Oracle redo log ~ PostgreSQL WAL
but with more details: 🧵👇🏻
In practice MSSQL transaction log ~= Oracle redo log ~ PostgreSQL WAL
but with more details: 🧵👇🏻
1. A transaction log must include:
- undo log
- redo log
- transaction boundaries
for A,C,I properties of ACID
It can be in memory but must be synced to disk at commit (#LogForceAtCommit) for the D property of ACID
- undo log
- redo log
- transaction boundaries
for A,C,I properties of ACID
It can be in memory but must be synced to disk at commit (#LogForceAtCommit) for the D property of ACID
2. For performance, writing data buffers to disk is deferred and reordered because random writes are slow. The changes lost after a crash can be rolled forward from the redo log to recover the on-disk state
