Serializability

Serializability
Basic Assumption – Each transaction preserves database consistency Thus, serial execution of set of transactions preserves database consistency.   A (possibly concurrent) schedule is serializable if it os equivalent to serial schedule (say, Transaction T1 follows Transaction T2 or T2 follows T1)   Different form of schedule equivalence gives rise to the notions of  1. ...

Recoverable and Cascadeless Schedules 36

Recoverability A recoverable schedule is one where, for each pair of Transaction Ti and Tj such that Tj  reads data item previously written by Ti   the commit operation of Ti  appears before the commit operation Tj .     Suppose that the system allows T9 to commit immediately after execution of read(A) instruction.Thus T9 commit before T8 does. Now suppose that T8 fails ...