Based on your readings and research, respond to the following: Multiuser databas

Question

Based on your readings and research, respond to the following:

Multiuser databases enable many people to access the data and manipulate it at the same time. Describe the different locking techniques to protect the data and why data locking is necessary. If locking did not exist, could multiuser databases exist? Why or why not?

Which data integrity problems are introduced by multiple users using the same database? Explain why these problems exist and how to protect against them.

Duplicate records can become troublesome in a database. How does the risk of duplicate records increase in multiuser databases?

Data is a valuable asset to most companies. Explain the different backup procedures for databases and explain when you would use them.

Describe the role of a database administrator (DBA). Make sure to include detail about transactions used by DBAs and locks that require DBA intervention.

Explanation / Answer

Locking technique: When multiple users access a database, there could be a chance that same data is accessed by several customers which may lead to inaccurate modificationmof data. In order to prevent such modification, locking technique is introduced.

Lock granularity: Defines the leavel upto which locking can be introduced.

Types of level:

Database level locks.

Table level locks.

Page level locks.

Row level locks.

Field level locks.

Types of locks:

(i) Binary locks.

(ii) Shared/exclusive locks.

(i)Binary locks have two states:

Locked and Unlocked.

Locked: If an object that is a data base, table, page or row is locked by a transaction no other transaction can use that object.

Unlocked: If an object is unlocked any transaction can lock the object for its use.

Shared/Exclusive locks:

Shared lock: Shared lock exists when concurrent transaction are granted read access on the basis of a common lock.

Excliusive Lock: An exclusive lock exists when access is reserved specifically for the transaction that locked the object.

Shared lock is issued when a transaction wants to read data from the data base.

Exclusive lock is issued when a transaction wants to update.

(b) If locking do not exist, multiple users can still access a database but that could lead to database inconsistency.

Data integrity: Data integrity is the overall completeness, accuracy and consistency of data. This can be indicated by the absence of alteration between two instances or between two updates of a data record, meaning data is intact and unchanged.

Types of integrity problems that may arise:

By using the above locking techniques, we can avoid such problems.

When multiple users try to access a database, many uers can update the database in same way and hence data duplicacy is resulted.

Following are the bakup techniques:

(i) Full backup

(ii) Incremental backup

(iii) Differential backup

(iv) Synthetic full backup

(v) Incremental-forever backup

(i) Full backup: It is a full copy of the entire data set. Although full backups arguably provide the best protection, most organizations only use them on a periodic basis because they are time consuming, and often require a large number of tapes or disk.

(ii) Incremental backup: Incremental backups were introduced as a way of decreasing the amount of time that it takes to do a backup. Incremental backups only backup the data that has changed since the previous backup. The primary disadvantage to incremental backups is that they can be time-consuming to restore.

(iii) Differential backup: A differential backup is similar to an incremental backup in that it starts with a full backup, and subsequent backups only contain data that has changed. The difference is that while an incremental backup only includes the data that has changed since the previous backup, a differential backup contains all of the data that has changed since the last full backup.

(iv) Synthetic full backup:

A synthetic full backup is a variation of an incremental backup. Like any other incremental backup, the actual backup process involves taking a full backup, followed by a series of incremental backups. But synthetic backups take things one step further.

What makes a synthetic backup different from an incremental backup is that the backup server actually produces full backups. It does this by combining the existing full backup with the data from the incremental backups. Synthetic full backups provide all of the advantages of a true full backup, but offer the decreased backup times and decrease bandwidth usage of an incremental backup.

(v) Incremental forever backup:

Incremental-forever backups are often used by disk-to-disk-to-tape backup systems. The basic idea is that like an incremental backup, and incremental-forever backup begins by taking a full backup of the data set. After that point, only incremental backups are taken.

What makes an incremental-forever backup different from a normal incremental backup is the availability of data. The process of restoring the incremental data becomes completely transparent and mimics the process of restoring a full backup.

Role of DBA(Database Administrator):

(i) Capacity planning

(ii) Installation

(iii) Configuring

(iv) Database design

(v) Migration

(vi) Security

(vii) Troubleshooting

(viii) Backup

(ix) Data recovery:

(i) Capacity planning: It is the process of determining the production capacity needed by an organisation. DBA performs this role of capacity planning for an organisation.

(ii) Installation: It is the act of making a program ready for execution. DBA performs this role by installing several softwares as needed by an organisation.

(iii) Configuration: It is the arrangement of functional units according to their nature, number and chief characterstics. DBA performs this role of configuring systems.

(iv) Database design: It is the process of designng a detailed model of a database. DBA performs this function of database design.

(v) Data migration: It is the process of transferring data between storage units or file formats.

(vi) Computer security: It is the process of protecting computer systems from theft or damage to their hardware, software or information.

(vii) Troubleshooting: It is a type of repairing or providing solution to a given task. This function is also generally performed by DBA.

(viii) Backup: Backup refers to copying and archiving of computer data for future use. This is also performed by DBA as explained above.

(ix) Data Recovery: Data recovery is the process of recovering damaged, corrupted, lost or formatted data from secondary storage, removable media or files when data stored in them cannot be accessed in a normal way.

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