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- WAL - write-ahead log | ||
- writing a lot of data to disk is expensive, which is why DBMSs persist a compressed version of the changes known as WAL | ||
- asynchronous snapshot | ||
- In this approach everything we write is kept in-memory and later on, asynchronously, it’s snapshot is synced/ written to the drive (persisted disk/ SSD/ Hard-drive) all at once. | ||
- AOF - append-only file | ||
- Very similar to the WAL strategy, It keeps track of only the changes happening. A very lightweight way of storing the changes and also gives the possibility of reconstructing the state of the system in case of failures. |
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- the process of ensuring persisting transaction permanently and do not accidentally disappear or get erased even during a database crash. | ||
- durability actions are slow because to make things durable that means you write to disk and writing to the disk is slow. | ||
- this means changes made by committed transactions must be persisted in a durable non-volatile storage. | ||
- [[database durability techniques]] | ||
- os cache | ||
- most of DBMSs bypass the os cache to ensure durability by fsync os which can be expensive and slow down commits |
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- can my inflight transaction see changes made by other transactions? | ||
- [[database read phenomenas]] | ||
- [[database isolation levels]] | ||
- | ||
- [[database isolation levels]] |