Features of three Oracle backup providers

In our actual application, there are three standard backups in the Oracle database that we often use. That is, EXPORT and IMPORT (EXPORT/IMPORT), cold backup, and hot backup. Exporting backup is a logical backup. This method involves reading a series of database logs and writing them into files. The reading of these logs is not related to the location.

Cold backup and hot backup are physical backups (also known as low-level backups) that involve the files that make up the database, but do not consider the logical content.

The following describes the three Oracle backup methods and their features:

(1) EXPORT/IMPORT (EXPORT/IMPORT)

EXPORT/IMPORT is used to remove data from/into the database.

1. EXPORT backs up the data in the database into a binary system FILE, which is called the "export dump file" and writes the generated database to the FILE again.

It has three modes:

A. User Mode: export data of all user objects and objects;

B. Table mode: export all or specified tables of the user;

C. entire database: export all objects in the database.

There are three types of backup:

A. complete export: backs up the entire database;

B. COMULATIVE ERPORT: Back up the data changed in the previous accumulation backup;

C. incremental (increamental export): The data changed after the last backup.

The EXPORT command can be performed interactively. For the specific meanings of each parameter, see the appendix.

When exporting an Oracle backup, we need to consider the consistency of the export. During the export process, each read is read from a table, therefore, although the export operation starts on its own when it is a feature, the reading time of different tables is different. Therefore, when the export operation starts to read a table, the data in the table is the exported data.

In this way, when most tables are connected by internal and external keywords, changes to these associated tables during the export process will lead to inconsistent export, we can schedule the export process without table operations. In addition, the restrictep consistent option in ORACLE ensures data consistency during export.

2. IMPORT:

The import process is the inverse process of the export. This command First reads the exported dump binary file and runs the file to restore the user and data of the object.

The method for executing the IMPORT command is related to the EXPORT scheme.

1. If the EXPORT implements the FULL mode scheme, all data objects, including tablespaces and data files, will be created during IMPORT, however, given the physical layout of the database, it is useful to create tablespaces and users in advance.

2. If the EXPORT uses the INCREMENTAL/CUMULATIVE mode, you must set the tablespace, user, and data file in advance.