Data security is an imperative aspect of any database system. It is of particular importance in distributed systems because of large number of users, fragmented and replicated data, multiple sites and distributed control.
Threats in a Database
Availability loss − Availability loss refers to non-availability of database objects by legitimate users.
Integrity loss − Integrity loss occurs when unacceptable operations are performed upon the database either accidentally or maliciously. This may happen while creating, inserting, updating or deleting data. It results in corrupted data leading to incorrect decisions.
Confidentiality loss − Confidentiality loss occurs due to unauthorized or unintentional disclosure of confidential information. It may result in illegal actions, security threats and loss in public confidence.
Measures of Control
The measures of control can be broadly divided into the following categories −
Access Control − Access control includes security mechanisms in a database management system to protect against unauthorized access. A user can gain access to the database after clearing the login process through only valid user accounts. Each user account is password protected.
Flow Control − Distributed systems encompass a lot of data flow from one site to another and also within a site. Flow control prevents data from being transferred in such a way that it can be accessed by unauthorized agents. A flow policy lists out the channels through which information can flow. It also defines security classes for data as well as transactions.
Data Encryption − Data encryption refers to coding data when sensitive data is to be communicated over public channels. Even if an unauthorized agent gains access of the data, he cannot understand it since it is in an incomprehensible format.
DATABASE RECOVERY IN DBMS AND ITS TECHNIQUES
DATABASE RECOVERY IN DBMS AND ITS TECHNIQUES: There can be any case in database system like any computer system when database failure happens. So data stored in database should be available all the time whenever it is needed. So Database recovery means recovering the data when it get deleted, hacked or damaged accidentally. Atomicity is must whether is transaction is over or not it should reflect in the database permanently or it should not effect the database at all. So database recovery and database recovery techniques are must in DBMS. So database recovery techniques in DBMS are given below.
Also See: Keys in DBMS Crash recovery:
DBMS may be an extremely complicated system with many transactions being executed each second. The sturdiness and hardiness of software rely upon its complicated design and its underlying hardware and system package. If it fails or crashes amid transactions, it’s expected that the system would follow some style of rule or techniques to recover lost knowledge.
DATABASE RECOVERY IN DBMS AND ITS TECHNIQUES
Classification of failure:
To see wherever the matter has occurred, we tend to generalize a failure into numerous classes, as follows:
Transaction failure
System crash
Disk failure
Types of Failure
Transaction failure: A transaction needs to abort once it fails to execute or once it reaches to any further extent from wherever it can’t go to any extent further. This is often known as transaction failure wherever solely many transactions or processes are hurt. The reasons for transaction failure are:
Logical errors
System errors
Logical errors: Where a transaction cannot complete as a result of its code error or an internal error condition.
System errors: Wherever the information system itself terminates an energetic transaction as a result of the DBMS isn’t able to execute it, or it’s to prevent due to some system condition. to Illustrate, just in case of situation or resource inconvenience, the system aborts an active transaction.
System crash: There are issues − external to the system − that will cause the system to prevent abruptly and cause the system to crash. For instance, interruptions in power supply might cause the failure of underlying hardware or software package failure. Examples might include OS errors.
Disk failure: In early days of technology evolution, it had been a typical drawback wherever hard-disk drives or storage drives accustomed to failing oftentimes. Disk failures include the formation of dangerous sectors, unreachability to the disk, disk crash or the other failure, that destroys all or a section of disk storage.
Storage structure:
Classification of storage structure is as explained below:
Classification Of Storage
Volatile storage: As the name suggests, a memory board (volatile storage) cannot survive system crashes. Volatile storage devices are placed terribly near to the CPU; usually, they’re embedded on the chipset itself. For instance, main memory and cache memory are samples of the memory board. They’re quick however will store a solely little quantity of knowledge.
Non-volatile storage: These recollections are created to survive system crashes. they’re immense in information storage capability, however slower in the accessibility. Examples could include hard-disks, magnetic tapes, flash memory, and non-volatile (battery backed up) RAM.
Recovery and Atomicity:
When a system crashes, it should have many transactions being executed and numerous files opened for them to switch the information items. Transactions are a product of numerous operations that are atomic in nature. However consistent with ACID properties of a database, atomicity of transactions as an entire should be maintained, that is, either all the operations are executed or none.
When a database management system recovers from a crash, it ought to maintain the subsequent:
It ought to check the states of all the transactions that were being executed.
A transaction could also be within the middle of some operation; the database management system should make sure the atomicity of the transaction during this case.
It ought to check whether or not the transaction is completed currently or it must be rolled back.
No transactions would be allowed to go away from the database management system in an inconsistent state.
No comments:
Post a Comment