Schedule in DBMS

What is Schedule? Serial Schedule, Non-Serial Schedule, Serializable Schedule

1. MCA, MSc(CS), PGDCA
PratibhaRashmi

2. Aschedulecontainsasetofinstruction
whichspecifytheorderoftheexecutionof
theinstructions.
Itcouldbethreetypes.
dbrau
Schedule
Serial Schedule
Non-Serial
Schedule
Serializable
Schedule

3. Theserialscheduleisatypeofschedulewhere
onetransactionisexecutedcompletelybefore
startinganothertransaction.
Aserialscheduledoesn’tallowconcurrency,only
onetransactionexecutesatatimeandtheother
startswhenthealreadyrunningtransactionstartswhenthealreadyrunningtransaction
finished.
IftherearetwotransactionsT1andT2
whichhavesomeoperations.Ifithasno
interleavingofoperations,thenthereare
thefollowingtwopossibleresults:

4. Execute all the operations of T1 which was
followed by all the operations of T2.
Here, Schedule A shows the serial schedule
where T1 followed by T2.

5. Execute all the operations of T2 which was
followed by all the operations of T1.
Here, Schedule A shows the serial schedule
where T2 followed by T1.

6. If interleaving of operations is allowed, then
there will be a non-serial schedule.
There are many possible orders in which the
system can execute the individual operations
of the transactions.of the transactions.
IftherearetwotransactionsT1andT2
whichhavesomeoperations.Ifithasno
interleavingofoperations,thenthereare
thefollowingtwopossibleresults:

7. Schedule C and Schedule D are the non-serial
schedules. Because It has interleaving of
operations.

8. A serializableschedule always leaves the
database in consistent state. Aserial
scheduleis always a serializableschedule.
However, a non-serial schedule needs to be
checked for Serializability.checked for Serializability.
A transaction schedule is serializableif its
outcome is equal to the outcome of its
transaction executing serially.

9. LetusconsiderI1andI2aretwoconsecutive
instructionsofT1andT2respectively.Boththe
instructionareoperatingonsamedataitemQ,these
instructionaresaidtobeconflictinginstructionifany
oneofthefollowinginstructionoccurs
simultaneously.
I1=read(Q)&I2=write(Q)I1=read(Q)&I2=write(Q)
I1=write(Q)&I2=read(Q)
I1=write(Q)&I2=write(Q)
Itmeansinboththeinstructiononeoperationis
writeoperationonthesamedataitemleadstothe
conflicts.
Conflictinginstructioncannotbeswap(interchange)
otherwisetheoperationoftheschedulewillbe
change.

10. Any execution of a set of transactions is
called as its ___________.
non-serial schedule
serial schedule
scheduleschedule
interleaved schedule
State true or false: If I = read(Q) and J =
read(Q) then the order of I and J does not
matter.
a) True
b) False

11. State true or false: If I = read(Q) and J =
write(Q) then the order of I and J does not
matter.
a) True
b) False
The _________is a type of schedule where one
transaction is executed completely before
starting another transaction.
a)serial schedule
b) non-serial schedule

12. What is scheduling in DBMS?
What is Schedule list the types of schedule?
What is serial schedule and serializableWhat is serial schedule and serializable
schedule?
What do you mean by conflict operations?

13. “Fundamentals of Database Systems” by R
Elmasriand S Navathe.
“An Introduction to Database Systems” by
BipinDesai
https://www. beginnersbook.com, https://www. beginnersbook.com,
http://Javapoint.com