The Oracle database file family includes seven types of core files: data files (.dbf): storing table and index data; control files (.ctl): recording database meta information; redo log files (.redo): recording transaction modification operations; parameter files (.pfile or .spfile): configuring database operation settings; archive log files (.arch): backing up redo log files; temporary files (.tmp): storing intermediate results of query and sorting; other auxiliary files: control file copy, data dictionary files, etc.

Oracle Database File Family: A Veteran's Talk

Alas, new here again? Oracle database file? This is a big question. Although it looks simple on the surface, there are many tricks inside! In this article, let me, the old guy, chat about these documents for you so that you can avoid detours. After reading it, you will have a clear understanding of the physical structure of Oracle database and will have a better understanding of the code when writing.

Start with the most basic one: data file (.dbf)

This thing is the home of data in your database. All tables and indexes must eventually be included in these data files. Imagine it is like a huge warehouse filled with all kinds of goods (data). Oracle will manage these "cargoes" skillfully so that you can quickly find whatever you need. It should be noted that the size of the data file is not infinite, and you have to plan it in advance, otherwise it will be troublesome if it is full. Expand capacity? Of course, it can, but frequent expansion will affect performance, so it is crucial to plan the space from the beginning. There was once a project that caused the database performance to decline sharply due to insufficient space planning of data files, and finally had to expand the capacity urgently. That taste was so sour.

Control file (.ctl)

This is the heart of the database! It records all important information about the database, such as the location of the data file, the location of the log file, the database name, etc. Without it, the database becomes a headless fly and can do nothing. Therefore, backing up control files is the top priority! I have seen many people crying because of damaged control files. It feels really bad. Back up a few more copies and place them in different places to be at ease.

Redo log file (.redo)

This thing is the safe of the database! It records the modification operations of all transactions in the database. In case the database crashes, with it, the data can be restored to its previous state. This is like writing a diary, recording what happens every day, so that it can be read later. The redo log file is also divided into online redo logs and archived redo logs. The online redo log is used for daily operation of the database, while the archived redo log is used for disaster recovery. Don't underestimate this small log file, it is a key guarantee for the stable operation of the database.

Parameter file (.pfile or .spfile)

This is like a database configuration file, which contains various parameters for the database operation, such as memory size, number of processes, etc. You can modify this file to adjust the performance of the database. However, modifying the parameter file is not a joke. If you are not careful, the database will crash. Therefore, you must make a backup before modifying and fully understand the meaning of each parameter. I once caused the database performance to drop by 50% due to an error in setting the parameter, which really makes people cry.

Archive log file (.arch)

This is a backup of redo log files for long-term data recovery. It is like a safe, storing precious data from a database. With it, even if the database completely crashes, it can still be restored to its previous state. However, archive log files will occupy a large amount of disk space, so it is necessary to reasonably plan the storage strategy of archive logs.

Temporary file (.tmp)

This thing is a temporary storage space for the database, used to store some temporary data. These data are usually intermediate results generated during query or sorting. The size of temporary files will vary with the use of the database, so you need to ensure that there is enough disk space to store temporary files.

Other documents

In addition to the above main database files, there are other auxiliary files, such as control file copies, data dictionary files, etc. Although these files are not so conspicuous, they are also crucial for the proper functioning of the database.

Remember, understanding these documents is not just rote memorization, but more importantly, understanding the relationship and role between them. Only in this way can we quickly locate and solve problems when we encounter them. This is not a paper talk, but the experience accumulated from countless practices. I hope these experiences can help you avoid detours. come on!

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