backup and recovery in database management system pdf

#Backup and recovery in database management system pdf software
#Backup and recovery in database management system pdf Offline

There are some common causes of failures such as, If the system crashes or failure occurs, then it is very difficult to recover the database.A database includes a huge amount of data and transaction.In stable memory, copies of the same non – volatile memories are stored in different places, because if the system crashes and data loss occurs, the data can be recovered from other copies.Stable memory is the third form of the memory structure and same as non-volatile memory.These files are backed up at regular intervals and the database is backed up once in a week. The log file includes all the information about the transaction being made. To overcome this problem the log files are backed up at regular intervals. The huge amount of data is an overhead to backup the whole database. If the system crashes or any failure occurs, the data would be copied from these tapes to bring the database up.ģ. The database is copied to secondary memory devices like Flash memory, hard disk, magnetic tapes, etc. The user will not know that there was a failure.Ģ. If the current database fails, then the system automatically switches to the remote database and starts functioning.

#Backup and recovery in database management system pdf Offline

The remote backup is also called as an offline backup because it can be updated manually. The database is updated with the current database and sync with data and other details. Remote backup creates a database copy and stores it in the remote network. To avoid data loss in the secondary memory, there are three methods used to back it up :ġ.

If the secondary memory crashes, whole data in the primary memory is lost and cannot be recovered.

Flash memory, hard disk, magnetic tapes etc.

These memories are huge in size, but slow in processing.

Non – volatile memory is the secondary memory.

To avoid data loss, create a copy of primary memory in the database with all the logs and buffers, create checkpoints at several places so the data is copied to the database.

If the primary memory crashes, then the whole data in the primary memory is lost and cannot be recovered.

When we fire a query, the database fetches a data from the primary memory and then moves to the secondary memory to fetch the record.

Primary memory is always faster than secondary memory.

RAM is a primary storage device which stores a disk buffer, active logs and other related data of a database.

In volatile memory, if the system crashes, then the data will be lost.

Volatile memory is the primary memory device in the system and placed along with the CPU.

Volatile memory can store only a small amount of data.

The storage of data is divided into three categories: Storage of DataData storage is the memory structure in the system. So the logical backup utilities allow DBA (Database Administrator) to back up and recover selected objects within the database.

Logical backup is used to restore the database objects into the database.

Logical backup extracts data using SQL from the database and store it in a binary file.

Operating system is an example of physical backup.

Physical backup extracts data from physical storage (usually from disk to tape).

It determines the speed and success of the recovery.

#Backup and recovery in database management system pdf software

Planning and testing backup helps against failure of media, operating system, software and any other kind of failures that cause a serious data crash.

It is a useful supplement to physical backups in many circumstances but not a sufficient protection against data loss without physical backups, because logical backup provides only structural information.

It includes backup of logical data like views, procedures, functions, tables, etc.

Logical Backup contains logical data which is extracted from a database.

Physical backup provides the minute details about the transaction and modification to the database.

Physical backups are the foundation of the recovery mechanism in the database.

It is a copy of files storing database information to some other location, such as disk, some offline storage like magnetic tape.Physical Backups are the backups of the physical files used in storing and recovering your database, such as datafiles, control files and archived redo logs, log files.If the original data is lost, then using the backup it can reconstructed.It protects the database against data loss.It is a safeguard against unexpected data loss and application errors.Database Backup is storage of data that means the copy of the data.