7.7- Uncommitted Dependency Problem in dbms | Need Of Concurrency Control In DBMS | Full Syllabus
7.7- Uncommitted Dependency Problem in dbms | Need Of Concurrency Control In DBMS | Full Syllabus
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Transactions & Concurrency Control In DBMS | Serializability | Recoverability | recovery System | Time stamp
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The Uncommitted Dependency Problem
This problem arises if any transaction Tj updates any variable v and allows retrieval or
updation of v by any other transaction but Tj rolled back due to failure. Consider the
transactions shown in Figure 8.4.
Transaction Ti Time Tansaction Tj
— —
— t
1 write(v)
— —
read(v) or write(v) t
2 —
— —
— t
3 —
— RollbackThe uncommited dependency problem.
At time t1, transaction Tj
, updates variable v which is read or updated by Ti
at time t2.
Suppose at time t3, Tj
is rollbacked due to any reason then result produced by Ti
is wrong
because it is based on the false assumption
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