Oracle Database four statuses, startup and Shutdown

There are a lot of learning materials on the Internet. Despite my determination to study oralce, there are still countless learning materials I can find. The popular fully open-source video "Han shunping-playing oralce" is almost done, take notes while reading. There are only a few questions about pl/SQL programming. Mr. Han is easy to understand, but he is not a bit cool and has little information for experienced people. The main purpose of watching his video is to consolidate the foundation here. There are too many things about oracle, and there are too many things to remember. Some things feel like they have been used, but they cannot be remembered or remembered correctly when used, this is the result of a poor foundation. Many oracle Daniel (ACE) thinks that it will be very fast to study later after the foundation is fixed, it is possible to become a senior DBA in three to five years. Of course, this foundation is not just to write a few SQL statements, or some operations, but also to read a lot of oralce official documents, but also step by step to read and experiment.
Www.2cto.com: Everything is hard at the beginning. Now I am at the beginning of my journey. Although difficult, I will stick to it with my perseverance for three to five years, be sure to make a name. Nowadays, information technology is too developed, and various technologies are too new and fast. As an ordinary programmer, it is almost impossible to keep up with a certain technology or keep thinking about new technologies. Less than two years of work, it is basically determined that you will go in the future, that is, oralce. A programmer will not wait until he is 30 years old to sigh and try again in the ocean of technology to find a suitable and promising technology, I lamented that fanghua was exhausted and had no inspiration.

We can see that most oralce ACE and ACE ctor considered DBA since, but they have achieved great success 10 years ago. They mentioned in their autobiography and interview records: I am not a genius, I do not have a lot of intelligence, but I am interested in oralce, and I will be indomitable. I have always insisted on achieving myself today. In particular, Mr. Yang Tingting, who seems to be a doctor, does not have much information about him on the Internet, but his blog is very famous in the oralce field, one article a day, rarely interrupted, so far, I have written more than 3000 articles. This persistence is not what the average person has done. With this persistence, nothing can be overcome. A small oralce is just invented by people, that's just decades. Learning is the specialty of our programmers. I insist that I have been training for many years. I may not be smart enough to learn oracle. The problem now is to believe in yourself and stick to it.
Www.2cto.com learned about Wang erwarm's video today. oralce starts and closes the video, and records it here to avoid forgetting it after time passes. First, oracle has four statuses: shutdown (completely closed), nomount (not loaded), mount (loaded), open (fully open ), it is better to use the command line to load these four statuses. The shutdown command is shutdown immediate (close immediately). Note: The order of database shutdown is different from that of Database loading. Nomount: in this state, oracle will open the parameter file, allocate the SGA, and open the background process. In this status, you can query the background process and instance information. For example, select * from v $ bgporcess; select * from v $ instance;
Www.2cto.com v $ parameter, v $ sga, v $ process, v $ session, v $ instance, and so on mount: in the mount status, oralce will be based on nomount, open the control file according to the settings of control_files. On the basis of nomount, the command to enter this state is: alter database mount in this state: the command that can be executed can be: select * from v $ tablespace; namespace select * from v $ datafile; data file select * from v $ database; database information
Www.2cto.com v $ controlfile, v $ database, v $ datafile, and v $ logfileopen: this status indicates that the database is fully open. On the basis of the mount, run the alter database open command, open all data files and redo logs based on the control file records on the mount. In this status, all operations within the permission range are enabled. Note: 1. In the shutdown status, you can directly jump to a certain status by using startup nomount | mount | open | force | restrict. Force is a force entry to the open state (no matter what the current state). restrict refers to the entry to the open state, but only users with the restricted session permission can log on. If you use startup without adding a parameter, it directly enters the open state. 2. If you use alter database *** to start oracle, you must start it in sequence, that is, nomount --> mount --> open. It cannot go beyond the level or in the opposite direction.