Ch15 3717

Chapter 15: Transactions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Transaction Concept ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

ACID Properties ,[object Object],[object Object],[object Object],[object Object],[object Object],To preserve integrity of data, the database system must ensure:

Example of Fund Transfer ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Example of Fund Transfer (Cont.) ,[object Object],[object Object]

Transaction State ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Implementation of Atomicity and Durability ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Implementation of Atomicity and Durability (Cont.) ,[object Object],[object Object],The shadow-database scheme:

Concurrent Executions ,[object Object],[object Object],[object Object],[object Object],[object Object]

Schedules ,[object Object],[object Object],[object Object]

Example Schedules ,[object Object]

Example Schedule (Cont.) ,[object Object],In both Schedule 1 and 3, the sum A + B is preserved.

Example Schedules (Cont.) ,[object Object]

Serializability ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Conflict Serializability ,[object Object],[object Object],[object Object]

Conflict Serializability (Cont.) ,[object Object],[object Object],[object Object],[object Object]

Conflict Serializability (Cont.) ,[object Object]

View Serializability ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

View Serializability (Cont.) ,[object Object],[object Object],[object Object],[object Object]

Other Notions of Serializability ,[object Object],[object Object]

Recoverability ,[object Object],[object Object],[object Object],Need to address the effect of transaction failures on concurrently running transactions.

Recoverability (Cont.) ,[object Object],[object Object]

Recoverability (Cont.) ,[object Object],[object Object],[object Object]

Implementation of Isolation ,[object Object],[object Object],[object Object],[object Object]

Transaction Definition in SQL ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Levels of Consistency in SQL-92 ,[object Object],[object Object],[object Object],[object Object],Lower degrees of consistency useful for gathering approximate information about the database, e.g., statistics for query optimizer.

Testing for Serializability ,[object Object],[object Object],[object Object],[object Object],[object Object],x y

Example Schedule (Schedule A) ,[object Object],[object Object]

Precedence Graph for Schedule A T 3 T 4 T 1 T 2

Test for Conflict Serializability ,[object Object],[object Object],[object Object]

Test for View Serializability ,[object Object],[object Object]

Concurrency Control vs. Serializability Tests ,[object Object],[object Object],[object Object]

Schedule 2 -- A Serial Schedule in Which T 2 is Followed by T 1

Schedule 5 -- Schedule 3 After Swapping A Pair of Instructions

Schedule 6 -- A Serial Schedule That is Equivalent to Schedule 3

Precedence Graph for (a) Schedule 1 and (b) Schedule 2

Illustration of Topological Sorting

Ch15 3717

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Ch15 3717