Serializability

Schedule Interleaves Transactions

A schedule is a time-ordered trace of transaction operations.

highlighted = computed this step

A schedule interleaves transactions

A schedule is a time-ordered trace of transaction operations. Each operation belongs to one transaction and may read or write an item. Note: the render is the source of operation order.

schedule trace\text{schedule trace}

Timeline

The compiled schedule has 4 operations across 2 transactions. Note: the vertical order is the actual trace order.

ops=4,txns=2\text{ops}=4,\quad \text{txns}=2

conflict-serializability is an exact SUFFICIENT criterion; a cyclic precedence graph is provably not conflict-serializable; view-serializability, lock scheduling, and recovery are beyond these tiny traces - no product claims.

Interleaved schedulestepT1T20R(A)1R(B)2W(A)3W(A) conflict-serializable: yes; topo: T1,T2T1T2

Summary

Schedules make transaction interleavings explicit before any graph is built. Note: conflict-serializability is exact here; view-serializability, locks, and recovery are deferred.

schedule first\text{schedule first}