The SQL provides a method for commit or roll back the data item into the database which is called as SQL support.
- Commit->It is a command that used to save the change that into the database as permanent we use commit on command prompt for saving the data.
- Roll back-> It is also the command of SQL but it uses to reject the changes of the data item from the data table we just write Rollback all command prompt for reflecting the change.
- Set transaction command-> It is a command that set the transaction process like read-only, read, write only, set transaction read to write on command prompt.
- Save point command->It is a command that uses for partially committed a transaction it means we can save the particular changes it related transaction of the data it, we use space point command and entity name for saving the data.
It is processed to copy the data from temporary storage and store into permanent storage like a floppy disk, magnetic tape etc. The back process basically uses to recover the information after the system failure. The system data also corrupt due to disaster attack like fire, flood, earthquake. The backup information must be kept synchronized with the primary copy of the database. The data is the important for any organization so need to store in the permanent storage area for restoring after failure. The system due to crash, system failure etc.
Types of backup
- Immediate backup-> It is a backup process that kept the data on a floppy disk, hard disk etc. The data can repair immediately after damage due to virus attack. This failure or network failure for immediate backup.
- Arrival backup-> It is a backup process that allows storing the data in permanent storage like internet services, magnetic tape etc that protect against disaster attack like flood, earthquake etc. the backup should be kept on the different side other than the system is functioning oracle application provide different step for backup the data records into secondary storage device.
The database system recovery
The data are processed in electronic device so need to manage the data protection. The backup process uses to protect information with different of the data record. Recovery is a process to transfer the data into system memory from the secondary storage device. The applications proceed recovery operation to restore the data item into the system from the backup area. There are different reasons for system failure like system crash, transaction error, disc failure, disaster attack etc destroyed the data item so need to recover the data from the backup area.
The data records are stored in different memory format for backup. The storage is defined as volatile and non-volatile format into as storage media.
Volatile storage media->
It is a storage media that store the information but the value is lost when the power ger switches off. The main memory, cash memory etc are the volatile storage the constructed with IC chip so access is too fast and the data store at processing time and last after switch off.
Non-volatile storage device->
It is a storage media that store the data as permanent and contains for a long time.
Stable storage device->
It is a storage device that stores the data as permanent and never lasts. This storage implement in the system where the data last is practically nil. Replicating the needed information in particular nonvolatile storage media and use the technique to get main information after failure the data storage.
The database provides different facilities to recover the data like checkpoint recovery manages and different properties of the database.
Dbms package provides different techniques to recover the data.
- Recovery using backup->
Mirroring – It is a process to create the copy of data record and maintain all line at the different stable storage device. We can recover the data from that storage after failure the record.
- Recovering using transaction log->
It is a recovering process that allows managing the data at different directives. A database divided into a number of stored in the current directory and use for processing. Before its all pages are copied in shadow directory. The shadow directory is also safe on disk and it helps to recover the information. The transaction executed on current directory and modify in some directory without a change in shadow directory.
Detached transaction action
The data are stored in a particular form and process on the base particular event detached transaction that is evaluated as a separate transaction lock acquired in previous activities. The transaction is executed on an occurrence of updating etc and also manage locking and errors. This method basically uses the distributed database to control more than one user and there processing. There are different action produce in a transaction like intermediate deferred and detached phase for controlling the recovery and backup or commit or rollback process.