섹션2. ACID - (1)

 

Transaction

     -A collection of queries 

     -One unit of work 

 

commit -> 디스크에 저장

ROLLBACK -> 롤백 

 

Transaction -> 읽기(read)도 포함 

 

 

 

8.Atomacity 

-All queries in a transaction must succeed.

-If one query fails, all prior successful queries in the transaction should rollback (even if there were successful queries)

-lack of atomacity ~> inconsistency 

 

 

9.Isolation

-Dirty reads   ->  not fully committed

-Non-repeatable reads  :  데이터베이스가 같은 거래를 반복 (같은 기능을 하는 서로 다른 쿼리)

-Phantom reads : 새로운 데이터가 삽입되고 commit될 경우. 

-Lost updates 

 

 

10.Consistency

-reading old version

-heal by eventual consistency (final result from raid) 

 

 

 

11.Durability 

-Changes made by committed transactions must be persisted in a durable non-volatile storage

-Durability techniques

   -WAL

   -Asynchronous snapshot

   -AOF