Serializability in DBMS
The backbone of the most modern application is the form of DBMS. When we design the form properly, then it provides high-performance and relative storage solutions to our application. In this topic, we are going to explain the serializability concept and how this concept affects the DBMS deeply. We also understand the concept of serializability with some examples. Finally, we will conclude this topic with an example of the importance of serializability.
What is Serializability in DBMS?
In the field of computer science, serializability is a term that is a property of the system that describes how the different process operates the shared data. If the result given by the system is similar to the operation performed by the system, then in this situation, we call that system serializable. Here the cooperation of the system means there is no overlapping in the execution of the data. In DBMS, when the data is being written or read then, the DBMS can stop all the other processes from accessing the data.
In the MongoDB developer certificate, the DBMS uses various locking systems to allow the other processes while maintaining the integrity of the data. In MongoDB, the most restricted level for serializability is the employee can be restricted by two-phase locking or 2PL. In the first phase of the locking level, the data objects are locked before the execution of the operation. When the transaction has been accomplished, then the lock for the data object is released. This process guarantees that there is no conflict in operation and that all the transaction views the database as a conflict database.
The two-phase locking or 2PL system provides a strong guarantee for the conflict of the database.
It can reduce the decreased performance and then increase the overhead acquiring capacity and then release the lock of the data. As a result, the system allows the constraint serializability for better performance of the DBMS. This ensures that the final result is the same as some sequential execution and performs the improvement of the operation that is involved in the database.
Thus, serializability is the system's property that describes how the different process operates the shared data. In DBMS, the overall Serializable property is adopted by locking the data during the execution of other processes. Also, serializability ensures that the final result is equivalent to the sequential operation of the data.
What is a Serializable Schedule?
Types of Serializability
In DBMS, all the transaction should be arranged in a particular order, even if all the transaction is concurrent. If all the transaction is not serializable, then it produces the incorrect result.
In DBMS, there are different types of serializable. Each type of serializable has some advantages and disadvantages. The two most common types of serializable are view serializability and conflict serializability.
1. Conflict Serializability
Conflict serializability is a type of conflict operation in serializability that operates the same data item that should be executed in a particular order and maintains the consistency of the database. In DBMS, each transaction has some unique value, and every transaction of the database is based on that unique value of the database.
This unique value ensures that no two operations having the same conflict value are executed concurrently. For example, let's consider two examples, i.e., the order table and the customer table. One customer can have multiple orders, but each order only belongs to one customer. There is some condition for the conflict serializability of the database. These are as below.
If there are two transactions that are executed concurrently, one operation has to add the transaction of the first customer, and another operation has added by the second operation. This process ensures that there would be no inconsistency in the database.
2. View Serializability
View serializability is a type of operation in the serializable in which each transaction should produce some result and these results are the output of proper sequential execution of the data item. Unlike conflict serialized, the view serializability focuses on preventing inconsistency in the database. In DBMS, the view serializability provides the user to view the database in a conflicting way.
In DBMS, we should understand schedules S1 and S2 to understand view serializability better. These two schedules should be created with the help of two transactions T1 and T2. To maintain the equivalent of the transaction each schedule has to obey the three transactions. These three conditions are as follows.
Testing of Serializability in DBMS with Examples
Serializability is a type of property of DBMS in which each transaction is executed independently and automatically, even though these transactions are executed concurrently. In other words, we can say that if there are several transactions executed concurrently, then the main work of the serializability function is to arrange these several transactions in a sequential manner.
For better understanding, let's explain these with an example. Suppose there are two users Sona and Archita. Each executes two transactions. Let's transactions T1 and T2 are executed by Sona, and T3 and T4 are executed by Archita. Suppose transaction T1 reads and writes the data item A, transaction T2 reads the data item B, transaction T3 reads and writes the data item C and transaction T4 reads the data item D. Lets the schedule the above transaction as below.
Let's first discuss why these transactions are not serializable.
In order for a schedule to be considered serializable, it must first satisfy the conflict serializability property. In our example schedule above, notice that Transaction 1 (T1) and Transaction 2 (T2) read data item B before either writing it. This causes a conflict between T1 and T2 because they are both trying to read and write the same data item concurrently. Therefore, the given schedule does not conflict with serializability.
However, there is another type of serializability called view serializability which our example does satisfy. View serializability requires that if two transactions cannot see each other's updates (i.e., one transaction cannot see the effects of another concurrent transaction), the schedule is considered to view serializable. In our example, Transaction 2 (T2) cannot see any updates made by Transaction 4 (T4) because they do not share common data items. Therefore, the schedule is viewed as serializable.
It's important to note that conflict serializability is a stronger property than view serializability because it requires that all potential conflicts be resolved before any updates are made (i.e., each transaction must either read or write each data item before any other transaction can write it). View serializability only requires that if two transactions cannot see each other's updates, then the schedule is view serializable & it doesn't matter whether or not there are potential conflicts between them.
All in all, both properties are necessary for ensuring correctness in concurrent transactions in a database management system.
Benefits of Serializability in DBMS
Below are the benefits of using the serializable in the database.
DBMS transactions must follow the ACID properties to be considered serializable. There are different types of serializability in DBMS, each with its own benefits and drawbacks. In most cases, selecting the right type of serializability will come down to a trade-off between performance and correctness.
Selecting the wrong type of serializability can lead to errors in your database that can be difficult to debug and fix. Hopefully, this guide has given you a better understanding of how Serializability in DBMS works and what kinds of serializability exist.
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