What is data backup and data recovery?

According to the backup size of database, there are four types of database backups. They are used in different occasions respectively:

1. Fully backups: This is Most common used for most people. It can backup the entire database, including user tables, system tables, indexes, views and stored procedures and all database objects. But it needs to spend more time and space, therefore,  we suggest you do a full backup once a week generally.

2. Transaction logs backups: Transaction log is a separate document, which records changes in the database, just only need to backup the modifies since the last backup in the database, so it only need very little time. In order to make the database robust, we suggest you backup the transaction logs an hour or even more frequently.

3. Differential backups: Designed to create backup copies of files that have changed since the last normal backup. The presence of the archive attribute indicates that the file has been modified and only files with this attribute are backed up.

4. Daily backups:Designed to back up files using the modification date on the file itself.

If a file has been modified on the same day as the backup, the file will be backed up. This technique doesn't change the archive attributes of files.

1. Cold backup, at this time, the database is closed to ensure the integrity of the database better.

2. Hot backup, the database is in operation, this method relies on a log of database.

3. Logical backup, use the software to extract data from the database and wrote the result in a file.

When the database has corruption or cause users incorrect manipulation, failures of operating system caused by the data cannot be seen or be read, lost. Engineers can read the data from the backup and make them recovery by some technological means.

Data backup and recovery is very important for database. You will want to have redundant backup sets that extend back for several backup periods.

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