'Serial Order' formal definition

In the Consistency and Isolation section of the Overview of Distributed Systems course, there is mention of things being in serial order. I couldn’t quite find a proper definition for this nor was it provided in the course.

I know it may seem obvious, but I want to know for certain what is meant by serial order. Does it mean things are order like a queue (FIFO) or is there some other type of inherent property that is considered when doing the ordering of data operations in a transaction?

Hi @Nomadic !!
In the context of distributed systems and databases, the term “serial order” refers to a specific type of ordering for transactions or data operations. It doesn’t necessarily mean things are ordered like a queue (FIFO), although there are similarities.

Serial order, also known as serializability, is a concept that ensures that the execution of concurrent transactions produces the same result as if they were executed one after the other in some sequential order. It guarantees that the outcome of concurrent executions is equivalent to a serial execution of those transactions.

In a serializable execution, the end result is the same as if each transaction had been executed in isolation without any overlap with other transactions. However, these transactions can still be executed concurrently for performance reasons, but their effects on the system must be equivalent to some serial order.

To achieve serializability, distributed systems and databases use various techniques, such as locking, timestamp ordering, and validation. These techniques help maintain the illusion that transactions are executed in a specific sequential order, even though they might actually be executed concurrently.

In summary, serial order in the context of distributed systems ensures that the outcome of concurrent transactions is consistent and equivalent to a specific sequential order, even though the actual execution might involve concurrency. It’s not strictly the same as a queue (FIFO), but it does guarantee a certain level of order and consistency in the system.
I hope it helps. Happy Learning :blush:

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