mysql
MySql design separates query processing with storage engine. MySql design has 3 layers. connection handling,query processing,storage engine Each connection gets its own thread from server and these threads are cached. MySQL parses queries and creates an internal structure(parse tree) and also caches the results of this query. locks types. read locks and write locks.read locks are shared,write locks ar exclusive. If the system spends too much time managing locks instead of storing and retrieving data,performance can suffer. write locks have higher priority than read locks. Lock granularity is an important decision in storage engine design.Ex: table locks ,row locks,row with mvcc In multi version concurrency control(MVCC) mechanism , a snapshot of the data is created and versioned. Isolation levels ,read_uncommitted,read_committed,read_repeatable,serializable. Transaction logging helps to make the requested changes in memory and transmit the changes to the actual storage later.As I/O t...