■ Ningbo Electric Power Bureau Xinmei
Database backup is a premise and foundation of data recovery. No data backup, once a database occurs or disaster, it will be difficult to recover. Common Oracle database faults include statement failures, user process faults, instance failures, user errors, and media failures. What kind of recovery can be done dependent on what kind of backup. As the DBA, the responsibility is responsible for maintaining the recoverability of the database from the following three aspects: (1) minimizing the number of expiration of the database, thereby keeping the database maximum; (2) When the database inevitably invalidate, The recovery time is minimized, so that the efficiency of the recovery reaches the highest; (3) After the database is invalid, make sure that the data is lost as possible or not, the data has the greatest recoverability. The author will discuss the backup and recovery of the database in Oracle8i as an example.
Oracle database backup recovery mode and characteristics
Oracle database backup is divided into physical backup and logical backups. Physical backup is a backup of database file copying, depending on the status of data in the backup, physical backups can be divided into cold backups and hot backups; export / import / import / import tools are used to perform logical backups.
Export Backup The data is extracted with the database definition, and saved as binaries in the internal format of Oracle; import (import) is used for opposite operations. The export backup mechanism cannot be provided to be recovered; and due to its way to use the query table, the speed is slower; the problem must be paid to the character set when exporting / imported; it is easy to erode; for databases, export / import operations The unsuccessful situation may be encountered.
Cold backup is a physical backup of a data file that is performed after the database is properly closed. When the database is turned off, copy all data files, control files, parameter files, password files, and redo log files, and redo log files to backup media. These files thus keep the full image when the data is closed.
Thermal spare (also known as an online backup) is a physical backup of the data that is running in the archivelog mode in the database. The hot backup that does not use Oracle RMAN is to set each table space to a backup state, then copy the corresponding data file, and then restore the table space to a normal state. The database can be used to make complete or incomplete recovery with the backup file and the archive log, which can be restored to any time point. Comparison of the characteristics of several backup methods described above
