Skip to main content

Schedule in DBMS

Schedule

A series of operation from one transaction to another transaction is known as schedule. It is used to preserve the order of the operation in each of the individual transaction.

Schedule in DBMS


1. Serial Schedule
The serial schedule is a type of schedule where one transaction is executed completely before starting another transaction. In the serial schedule, when the first transaction completes its cycle, then the next transaction is executed.

For example: Suppose there are two transactions T1 and T2 which have some operations. If it has no interleaving of operations, then there are the following two possible outcomes:
  1. Execute all the operations of T1 which was followed by all the operations of T2. 
  2. Execute all the operations of T1 which was followed by all the operations of T2. 

  • In the given (a) figure, Schedule A shows the serial schedule where T1 followed by T2.
  • In the given (b) figure, Schedule B shows the serial schedule where T2 followed by T1.

2. Non-serial Schedule
  • If interleaving of operations is allowed, then there will be non-serial schedule.
  • It contains many possible orders in which the system can execute the individual operations of the transactions.
  • In the given figure (c) and (d), Schedule C and Schedule D are the non-serial schedules. It has interleaving of operations.

3. Serializable Schedule
  • The serializability of schedules is used to find non-serial schedules that allow the transaction to execute concurrently without interfering with one another. 
  • It identifies which schedules are correct when executions of the transaction have interleaving of their operations.
  • A non-serial schedule will be serializable if its result is equal to the result of its transactions executed serially.

Schedule in DBMS

Schedule in DBMS

Schedule in DBMS

Schedule in DBMS



Here,

Schedule A and Schedule B are serial schedule.

Schedule C and Schedule D are Non-serial schedule.
Labels:

Comments

Post a Comment

Please do not enter any spam link in the comment box.

Popular posts from this blog

Concurrency Control

What is Concurrency Control? Concurrency Control in Database Management System is a procedure of managing simultaneous operations without conflicting with each other. It ensures that Database transactions are performed concurrently and accurately to produce correct results without violating data integrity of the respective Database. Concurrent access is quite easy if all users are just reading data. There is no way they can interfere with one another. Though for any practical Database, it would have a mix of READ and WRITE operations and hence the concurrency is a challenge. DBMS Concurrency Control is used to address such conflicts, which mostly occur with a multi-user system. Therefore, Concurrency Control is the most important element for proper functioning of a Database Management System where two or more database transactions are executed simultaneously, which require access to the same data. Potential problems of Concurrency Here, are some issues which you will likely to face wh...
Post a Comment
Read more

Joins in DBMS

DBMS Joins: Inner, THETA, Outer, Equi Types of Join Operations Join in DBMS is a binary operation that allows you to combine join product and selection in one single statement. The goal of creating a join condition is that it helps you to combine the data from two or more DBMS tables. The tables in DBMS are associated using the primary key and foreign keys. Types of Join There are mainly two types of joins in DBMS: Inner Joins: Theta, Natural, EQUI Outer Join: Left, Right, Full Inner Join Inner Join is used to return rows from both tables which satisfy the given condition. It is the most widely used join operation and can be considered as a default join-type An Inner join or equijoin is a comparator-based join which uses equality comparisons in the join-predicate. However, if you use other comparison operators like “>” it can’t be called equijoin. Inner Join further divided into three subtypes: Theta join Natural join EQUI join Theta Join Theta Join allows you to merge two tables ba...
Post a Comment
Read more

DBMS Keys

DBMS Keys KEYS in DBMS is an attribute or set of attributes which helps you to identify a row (tuple) uniquely in a relation(table). They allow you to find the relation between two tables. Keys help you uniquely identify a row in a table by a combination of one or more columns in that table. Key is also helpful for finding unique record or row from the table. Database key is also helpful for finding unique record or row from the table. Example: Employee ID FirstName LastName 11 Andrew Johnson 22 Tom Wood 33 Alex Hale In the above-given example, employee ID is a primary key because it uniquely identifies an employee record. In this table, no other employee can have the same employee ID. Here are some reasons for using sql key in the DBMS system. Keys help you to identify any row of data in a table. In a real-world application, a table could contain thousands of records. Moreover, the records could be duplicated. Keys in RDBMS ensure that you can uniquely identify a table record despite ...
Post a Comment
Read more