Oralce database disaster recovery

Oralce DatabaseFaults encountered during the operation are very difficult and need to be solved in a timely manner. Otherwise, they will have a bad impact on everyone's work, this requires you to master some Oralce database disaster recovery methods. With the rapid development of office automation and e-commerce, enterprises are increasingly dependent on information systems. As the core of information systems, databases play an important role. Especially in industries that require high data reliability, such as banks, securities, and telecommunications, the loss will be very serious if unexpected shutdown or data loss occurs. To this end, the database administrator should formulate detailed database backup and disaster recovery policies based on specific business requirements, and conduct strict tests on each possible situation by simulating faults, only in this way can we ensure high data availability. Database backup is a long-term process, and recovery is only performed after an accident. recovery can be seen as a backup inverse process, the degree of recovery depends largely on the backup situation. In addition, whether the steps taken by the database administrator during recovery are correct or not directly affects the final recovery result. This article mainly provides the corresponding recovery methods for Oracle Database faults, for your reference only.

To have a clear understanding of Oracle database backup and recovery, first of all, it is necessary to have a full understanding of several running statuses of the database. Oracle databases run in three statuses:

L Nomount not installed) Oracle only reads the configuration information in the INI file and initializes the SGA zone.

L Mount installation) in addition to reading the INI file, Oracle also needs to read the control file and obtain information about the physical structure of the database.

L Open) The database should check that all files are at the same time point, recover the error, roll back the unfinished transactions, and finally allow the user to access.

There are three types of Database Backup: Cold backup, hot backup, and logical backup;

Database Backup is not the focus of this Article. Here we will only give a brief introduction. Oracle Database Backup mainly includes:

L Cold Backup) refers to the full Backup of the database when the database is closed. The Backup content includes all data files, control files, online log files, and INI files.

L Hot Backup refers to backing up data files and control files when the database is running. To use Hot Backup, you must run the database in Archive Log Archive mode.

L Export logical backup) This is the simplest backup method. It can be exported based on a table in the database, a user, or the entire database, and supports three methods: full, accumulative, and incremental. In this way, the database must be in the open state, and the consistency of exported data cannot be guaranteed if the database is not in the restrict state.

Database recovery can be divided into two categories: full recovery; Incomplete recovery;

Full recovery refers to restoring the database to the time point of failure without losing any data. Incomplete recovery refers to restoring the database to a time point before a fault occurs. All changes after this time point will be lost. If there are no special requirements, we recommend that you use full recovery whenever possible.

The restoration process of the Oracle database is divided into two steps. First, all the retries stored in the redo log file are applied to the data file, and then all uncommitted transactions in the Redo are rolled back, in this way, all the data will be restored to the time of the disaster. Database recovery can only be used to redo data files before a fault occurs, restoring them to the time of failure, rather than rolling back the data files to a previous time point. For example, we have a database backup of 2001/1/1. When 2001/5/1, we find that data in the database is in disorder and want to restore the database to the status of 2001/4/30, we can only restore the database backup of 2001/1/1 and then use the redo record on it to roll back to the status of 2001/4/30, instead of rolling back the database of 2001/5/1 to 2001/4/30.

To design a database recovery plan for the system, we first classify possible errors. Oracle database errors are classified into five categories:

L SQL statement failure

L thread failure

L instance failed

L user operation failed

L storage device failure

We have summarized so many faults that may occur during the operation of the Oralce database. I believe that through the above learning, we have mastered how to handle faults in the Oralce database, if you encounter similar problems in your future work, you can easily solve them. I hope the content mentioned above will be helpful to you.