Distributed Systems Flashcards
What CAP from the CAP Theorems stands for?
C - consistency
A - Availability
P - Partition tolerance
What does Consistency mean in the CAP Theorem?
Consistency property guarantees that every Read request receives the most recent write or an error
What does Availability mean in the CAP Theorem?
Availability property guarantees that every request receives a non-error response, but without the guarantee that it contains the most recent write
What does Partition Tolerance mean in the CAP Theorem?
Partition Tolerance property guarantees that the system continues to operate despite an arbitrary number of messages being dropped or delayed by the network between nodes
What is ACID for RDBMS?
ACID stands for Atomicity, Consistency, Isolation, and Durability. These 4 properties of DB transactions are intended to guarantee validity even in the event of errors, power failures, etc.
What is Atomicity property in the ACID?
Atomicity requires that a transaction which consists of several statements either complete or rollback completely, thus making the multiple statements succeed or fail as an atomic unit. A failure of a single statement should cause the entire transaction to fail. Partially finished transactions should never be visible, since a statement could subsequently fail, thus causing the entire transaction to rollback.
What is Consistency property in the ACID?
Consistency requires that a transaction bring the database from one valid state to another that adheres to all constraints. For example, RDBMS’s require that a foreign key either point to an existing parent or be NULL. So if a transaction tries to insert a child that points to a parent, such as “Brad Vander Zanden”, then “Brad Vander Zanden” must be verified to exist and must continue to exist until the transaction has been completed.
What is Isolation property in the ACID?
Isolation requires that transactions should not interfere with each other. The system should guarantee the same results if the transactions are executed in parallel or sequentially. In practice most RDBMS products allow modes that trade off isolation against performance.
What is Durability property in the ACID?
Durability requires that once a transaction has been committed, it will remain committed even in the case of a system failure (e.g., power outage or crash). This usually means that completed transactions are recorded in non-volatile memory, such as on a disk or solid-state memory.
