Talking about Oracle EXP backup

For the sake of database data security, the exp command is no stranger to most Oracle users (especially database administrators). This exp command can complete various backup of database data, for example, full database, specific user, and specific table. Similar Commands include expdb. The only difference between expdb and expdb is that the exported data size is displayed while exp does not. The main analysis here is not how to use the exp command, but whether there is a problem with the data exported by the exp command.

When is exp most suitable for data backup? How can I back up an international application (or communication application) database?

To answer the first question, you need to understand the following. We know that the oracle database startup process includes the following steps:

1. startup nomount reads the oracle spfile and initializes the database instance;

2. alter database mount reads control files ,;

3. alter database open loads the database instance according to the configuration of the database Control File, checks and processes the database Consistency Based on the log file information stored in the control file, and recovers the instance, after the database is loaded successfully, it provides external services.

When the database is backed up in the open state using the exp method, the data block we backed up may also be written, resulting in a difference between the data block backed up and the actual data block, data consistency, that is, data ambiguity. We understand that the data backup exported at a certain time point can reflect the data information at the time of backup. That is to say, the backup data is a snapshot of the data at that time, but this is not actually the case. To maximize the consistency of backup data, we often perform database backup in the early morning (at this time, business operations will be rare or even absent, this explains why database backup should be performed in the early morning. We do not have a high requirement on data consistency during testing and development, as long as we meet our minimum requirements (the development application can run normally without or without business data.

How does one back up an international application (or communication application) database? Global access is required, and business data is generated at random times. data consistency problems exist in data backup at any time. To solve this problem, you need to use rman provided by oracle for backup. What is the difference between rman and exp? Exp backs up database objects and only copies the data. configuration files, control files, and log files are not backed up. Such backups are usually the most dangerous; exp backup is simple, and rman backup is complicated (requires a lot of knowledge and many syntax rules ).

Based on the above analysis, we recommend that you use rman for database backup later. You need to back up important database files, configuration files, control files and log files, and perform irregular verification on backup files to ensure that the backup files are valid;

The above is a personal analysis summary, for reference only. If there are errors or incomplete parts, you can add them later. If there are deficiencies, you can correct them.