What is the difference between cold backup and hot backup?

What is the difference between cold backup and hot backup?

Cold backup

Cold backup occurs when the database has been shut down normally. When it is shut down normally, it will provide us with a complete database. A cold backup is a way of copying critical files to another location. Cold backup is the fastest and most secure method for backing up Oracle information. The advantages of cold backup are:

1. It is a very fast backup method (just copy the files)

2. Easily archive (just copy)

3. Easily restore to a certain point in time (just copy the files back)

　4. Can be combined with the archiving method to restore the database in its "best state".

　5. Low maintenance, high security.

Hot backup

Hot backup is a method of backing up the database in archivelog mode while the database is running. Therefore, if you have a cold backup from last night and today's hot backup file, you can use these data to restore more information when a problem occurs. Hot backup requires the database to operate in Archivelog mode and requires a large amount of archive space. Once the database is running in the archivelog state, a backup can be made. The hot backup command file consists of three parts:

　1. Data file, table space and table space backup.

　(1) Set the table space to the backup state

　(2) Back up the data files of the table space

　(3) Restore the table space to the normal state

2. Back up archive log files

　(1) Temporarily stop the archive process

　(2) Log files in the archive rede log target directory

　(3) Restart archive Process

　(4) Back up the archived redo log file

　3. The advantages of using the alter database bachup controlfile command to back up the control file hot backup are:

　1. It can be backed up at the table space or database file level, and the backup time is short.

2. The database is still available during the backup.

　3. Achieving second-level recovery (recovery to a certain point in time).

　4. Can restore almost all database entities

　5. Recovery is fast and in most cases the database is still working when restored.

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