Serial Schedules in Database Transactions

Serial Schedules in Database Transactions, what is serial schedule?, Example for serial schedules, Define serial schedule

Serial Schedule

Schedule - A schedule is a list of operations (read, write, commit, abort, checkpoint, calculation – we mostly consider the read and write operations) that are performed by various concurrently (simultaneous) executing set of transactions. For further information refer the Transaction Schedules page.

Serial Schedule - A serial schedule is a schedule in which all the instructions belong to a transaction complete before the other transactions. That is, the transactions are executed one after the other without interleaving.

For example, assume that a schedule S with two transactions, namely, T1 and T2. If all the instructions of T1 are executed before T2 or all the instructions of T2 are executed before T1, then S is said to be a serial schedule.

Example:

Table 1, 2, and 3 show some examples of serial schedules.

In schedule S1, T1 completes before T2.

Transaction T1	Transaction T2
read(A); A := A – 5; write(A); read(B); B := B – 5; write(B);	read(A); temp := A * 0.1; A := A – temp; write(A); read(B); B := B + temp; write(B);

Table 1: Schedule S1

In schedule S2, the execution order is T3, T1, T2

Transaction T1	Transaction T2	Transaction T3
read(A); A := A – 5; write(A); read(B); B := B + 5; write(B);	read(A); temp := A * 0.1; A := A – temp; write(A); read(B); B := B + temp; write(B);	read(C); temp1 := C * 0.5; C := C + temp1; write(C); read(D); temp2 := D * 0.5; D := D + temp1; write(D);

Table 2: Schedule S2

In schedule S3, T2 completes before T1.

Transaction T1	Transaction T2
read(A); A := A – 5; write(A); read(B); B := B – 5; write(B);	read(A); temp := A * 0.1; A := A – temp; write(A); read(B); B := B + temp; write(B);

Table 3: Schedule S3

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