Data Replication in Mobile Computing
Data Replication
Data Replication in mobile computing means the sharing of information to ensure data consistency between software and hardware resources connected via the internet, to improve reliability, availability, fault-tolerance, and accessibility of data.
In simpler terms, data replication is the process of storing different copies of the database at two or more sites in order to improve data availability in less time and at a cheaper cost.
Data replication in mobile computing is a popular fault tolerance technique for distributed databases.
Advantages of Data Replication
In modern mobile computing, scenario data replication has been adopted as an efficient way to ensure data availability, integrity, and an effective means to achieve fault tolerance.
Data replication not only ensures the availability of the data but also minimize the communication cost, increase data sharing, and enhance the security of sensitive data.
Data replication in mobile computing also determines when and which location to store the replica of data, controlling different data replicas over a network for efficient utilization of the network resources.
Data Replication Benefits
Important benefits of data replication are as below-
- Reliability − Data replication provides the reliability of data. In case of failure of any site, the database system continues to work since a copy is available at another site(s).
- Reduction in Network Load − Since local copies of data are available through data replication. Therefore, query processing can be done with reduced network usage, particularly during prime hours.
- Data updating can be done at non-prime hours – Due to data replication data can be updated easily.
- Quicker Response − Availability of local copies of data ensures quick query processing and consequently quick response time.
- Simpler Transactions − Transactions require less number of joins of tables located at different sites and minimal coordination across the network. Thus, they become simpler in nature.
Disadvantages of Data Replication
- Increased Storage Requirements − Maintaining multiple copies of data is associated with increased storage costs.
The storage space required is in multiples of the storage required for a centralized system.
- Increased Cost and Complexity of Data Updating − Each time a data item is updated, the update needs to be reflected in all the copies of the data at the different sites.
This requires complex synchronization techniques and protocols.
- Undesirable Application – Database coupling − If complex update mechanisms are not used, removing data inconsistency requires complex co-ordination at the application level.
Data Replication in Mobile Computing
Data replication is the process of making copies of data stored on various sites in order to improve reliability, efficiency, robustness, simpler transaction, fault tolerance, and reduce network load.
Goals of data replication
Data replication is performed with the purpose of
- Increasing the availability of data.
- Speeding up the query evaluation.
Types of data replication
There are two types of data replication
1. Synchronous Replication
In synchronous replication, the replica of the database is modified immediately after changes are made in the relation table.
So there is no difference between the original data and the replicated data table.
2. Asynchronous replication
In asynchronous replication, the replica will be modified after commit action is fired on to the database.
Replication Schemes
The three replication schemes are as follows:
- Full Replication scheme
In full replication scheme, the database is available at all the locations to ease the user in the communication network
Advantages of full replication
- It gives high availability of data. In this scheme, the database is available at each location.
- It supports faster execution of queries.
Disadvantages of full replication
- In a full replication scheme, concurrency control is difficult to achieve in full replication.
- During updating each and every side need to be updated therefore update operation is slower.
- No Replication
No replication means each fragment is stored exactly at one location only.
Advantages of no replication
- Concurrency can be easily minimized.
- Easy recovery of data becomes easy.
Disadvantages of no replication
- Poor availability of data.
- Slows down the query execution process, because multiple clients are accessing the same data at the same server.
- Partial replication
A partial replication scheme means only part of the or data fragments are replicated.
