Transactions Flashcards
What are the ACID properties of transactions?
Atomicity, Consistency, Isolation and Durability
What does atomicity of a transaction refer to?
Indivisiblity, all or nothing
What does consistency in transactions refer to?
Mapping consistent states to other consistent states the same way
What does isolation in transactions refer to?
Independence from other transactions
What does durability in transactions refer to?
The permanent recording of successful transactions
What is a Lost Update?
When a write is lost as it is overwritten by a later write
What is a dirty read?
The reading of an uncommited write
What is a non-repeatable read?
Reading different values of the same variable in one transaction
What is a phantom read?
Reading different rows of the same table in one transaction
What are the 4 isolation levels?
Read uncommited, read commited, repeatable read and serializable
Which read errors does read uncommited solve?
Lost update
Which read errors does read commited solve?
Lost update, dirty read and phantom read
Which read errors does repeatable read solve?
Lost update, dirty read, non repeatable read, and phantom read
Which read errors does serializable solve?
Lost update, dirty read, non repeatable read, and phantom read
