The Oracle tutorial you are looking at is the security policy for Oracle databases. ----Oracle is a relational database management system, which has powerful function and excellent performance, and occupies an important position in today's large database management system. In the MIS system developed by us, we choose the Oracle7.3 database. Under normal circumstances, Oracle database will ensure data security, stability, provide users with correct data, but due to computer system failures (hardware, software, network and system failure) affect the operation of the database system, affecting the correctness of data in the database, and even destroy the database, All or part of the data in the database is lost and the entire system is paralyzed. Therefore, how to ensure the security of Oracle database is an important part of the whole MIS system security.
Security Policies----Oracle databases include backup and recovery of databases, and user role management.
----One, the structure used by the database backup
----Oracle databases use several structures to protect data: Database fallback, logging, rollback segments, and control files.
----1. Database fallback consists of the operating system fallback of the physical files that make up the Oracle database. When the media failure of the database recovery, the use of backup files to recover corrupted data files or control files.
----2. Each Oracle database instance provides a log that records all changes made in the database. Each running Oracle database instance has a corresponding online log that works with the Oracle background process LGWR to immediately record all changes made to the instance. Archive (offline) logging is optional and an Oracle database instance can form an online log archive once the online log fills up. Archived online log files are uniquely identified and merged into an archive log.
----3. The rollback segment is used to store the old value of a modified value for a transaction in progress (for uncommitted transactions) that is used to undo any uncommitted modifications during database recovery.
----4. Control files, typically used to store the state of the physical structure of the database. Some state information in the control file is used to boot Oracle during instance recovery and media recovery.
----Two, online log
----Each instance of an Oracle database has an associated online log. An online log consists of multiple online log files. Log entries (Redo entry) are filled in on-line log files (online redo log file), and log entries record data to refactor all changes made to the database.
----Three, archive log
An archive log (archived redo log) is established----Oracle wants to archive the filled online log filegroups. The following are useful for database backup and recovery:
----1. Database backup and online and archived log files ensure that all submissions are recoverable in the operating system and disk failures.
----2. In the case of database open and normal system use, if the archive log is permanently saved, online backup can be done and used.
----database can be run in two different ways: Noarchivelog or Archivelog mode. When a database is used in a noarchivelog manner, it is not possible to archive online logs. If the database runs in Archivelog mode, you can implement an online log archive.
----Four, Oracle backup features
----Oracle backups include logical and physical backups.
----1. Logical backup
A logical backup of----database consists of reading a database recordset and writing the recordset to a file.
----(1) output (export) output can be an entire database, a specified user, or a specified table.
----(2) input (import) Enter the binary dump file created by the output into and execute its command.
----2. Physical backup
----physical backups contain files that make up the database, regardless of their logical content.
----Oracle supports two different types of physical file backups: Offline backup (offline Backup) and online backup (on line Backup).
----(1) Offline backup
----Offline backup to back up the following files when the database has been shut down properly and the database is "offline":
All data files
All control files
All online logs
Init.ora (optional)
----(2) Online backup
----Online backup can be used to back up any databases that operate in Archivelog mode. In this way, the online log is archived and a complete record of all jobs is established within the database.
----The online backup process has powerful features. First, a complete point-in-time (point-in-time) recovery is provided. Second, allow the database to remain open while the file system is backed up.
Comparison of characteristics of----backup methods
Mode type recovery feature
Export logic can restore any database object to the state of the output
Offline Backups Physics can restore the database to a shutdown state: If the database is running in Archivelog mode, it can revert to any point in time.
Online Backups Physics can restore the database to any point in time
----v. Role management for Oracle databases
----The basic measures taken by Oracle database systems to take advantage of role management database security are:
Prevents non-Oracle users from registering with the Oracle database and illegally accessing the database by verifying the user name and password.
Grant users certain permissions to restrict the user's power to manipulate the database.
Grants user access to the database entity, and prevents users from accessing unauthorized data.
The database entity Access Audit mechanism is provided so that the database administrator can monitor the data access and system resource usage in the database.
Use the view mechanism to restrict access to the rows and columns collection of the base table.
Security strategy of Oracle database in----MIS system
----Because Oracle database backups are available in three ways, each with different recovery characteristics, you should integrate database and file system backups, integrate logical and physical backups.
----One, backup strategy
1. At the operating system level, with a large-capacity disk array, each database file is automatically distributed to each physical disk by disk image technology. In this way, when a disk is physically damaged, the operating system automatically raises the image disk to replace the failed disk, ensuring that the database is running properly.
Because we are using a dual server, keep a backup database on another server. The backup database has the same parameter state as the database in use, so that in the case of a database failure, only minimal recovery is required to minimize recovery time.
Maintain multiple backup of control files on multiple different physical disks. Control files are used to boot Oracle during database recovery, so maintaining multiple backup of control files ensures that the available control files can be used for database recovery after a disk failure occurs.
Make the database run in Archivelog (archived) mode, and the archive log is stored on a logical disk in another image.
Perform an online backup operation every night, backing up all data files, all archived log files, and a control file.
An export operation is performed once a week.
----second, recovery strategy
----1. Instance failed
----recovery from an instance failure is automatic. Instance failures are typically caused by a server failure, restarting the server after the database instance fails, starting the database, Oracle checking data files and online log files, and synchronizing all files to the same point in time.
----2. Disk failed
----If the control file is lost, just close the database and copy one from the place where the control file is kept.
----If the data file is missing, use the online backup from the previous night to recover, as follows:
----1) The missing files are located in the original location from the backup.
----2) Loading the database
----3) Restore the database
----4) Open the database
----3. Error deleting or modifying an object
----In this case, it is generally desirable to return back to the point in time before the error occurred. This is called Point-in-time recovery. The steps to complete the recovery are as follows:
----1) from the current database output (export), input (import) to the standby database, keeping the standby database consistent with the current database.
----2) Roll forward the standby database to the point in time before the error occurred.
----3) To export the logical object affected by the error from the standby database.
----4) Enter those affected objects into the current database using the output file produced in the previous step.
----Third, User role management
----1. Classify all clients by job nature and grant different user roles to each.
----2. For different user roles, grant access to different database objects according to the data source they use.
----based on the above security policy, can prevent illegal users access to the database, restrict the legitimate user to manipulate the database permissions; You can make the database not lose any data after the failure occurs, and can quickly restore the database to the point before the failure occurred, Maximize the security of the data and the continuous operation of the entire system.
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