How Oracle works

How Oracle works
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A man named Sid is eager to take, save, and organize photos. Sid's wife is Debbie, who has three sons: Logan, Archie, and Chuck. He has a very big house with the Master Simon and the servant Pam. I will introduce his family, his house, and his hobbies: shooting, collecting, and showing off his photos.
Now, Sid lives happily-family, friends, and holidays. He takes photos from time to time. In fact, he always carries his camera with him. He doesn't want to miss anything. Breakfast, lunch, and dinner are all taken. When the children go home from school, they receive greetings from their father. When the children do their homework, the shutter of the camera keeps ringing. At the baseball game, each of my son Archie's throws were taken. At the school dance, Chuck's father captured every slow dance step and talked to him next to the soda machine. His dog, Sadie, is the most photographed dog in the world.
He and his family collect millions of photos. Some photos have been destroyed, and some have undergone changes. Sid has a magic system to process these photos. Let me tell you something about his family, his house, and how he and his family are committed to developing, organizing, and protecting all these photos.
Sid is taken with a special camera. Each time a camera is taken, a photo and a negative film are generated at the same time. He never used film (a sci-fi technology ). The photo is pasted on the walls of the room, while the negatives are stored in a safe place.

1.1.1 Sid's home
Have I introduced Sid's home? Well. There are very big pictures everywhere. Because there are too many photos, Sid must look for places to place them. Some photos are hung on the walls, some are hidden in the album, some are inserted into the clipboard, and some are placed in a box in the storage room and won't be glanced at again. All these photos are put somewhere in his home. He calls the place where the photos are stored as a "photo space ". A photo space may be a room with many walls or a clipboard with many pages. A room is a logical unit of photo storage. The walls in the room are the physical structure of the photos stored in the photo space.

1.1. 2 Debbie's anecdote
Because Sid is busy shooting and processing photos, he doesn't have enough energy to store them-it's her wife's job. The full name of Debbie is Debra wrider. She printed dbwr on her t-shirt-a family tradition-to label everything.
It is a huge task to put all these photos in a well-organized manner, but Sid and Debbie have already built a system. After the video is taken, Sid places all the photos on a specific shelf in the kitchen. The specific shelf is called "db_buffer_cache ". Debbie often checks the shelf to see if there are any new photos on it. During the day, she placed the photos retrieved from the shelf into the corresponding photo space. As a matter of fact, at a baseball or school dance, Sid is making photos too fast. So that Debbie could barely keep up. This is a special situation where Sid takes a photo and places it on that particular shelf. Debbie places the photo in the clipboard, hangs it on the wall, or inserts it into the album.
When Sid enters the kitchen with photos and negatives, there may be a conversation between him and his wife:
Sid: "Dear, guess what I brought you back ?"
DEBBIE: "You have taken a lot of photos, have you? You know how much I like organizing photos ."
Sid: "Of course, Archie's baseball team won the last game. He won the second base in the ninth round. I shot all of them ."
DEBBIE: "That's great. Those photos are placed in the sports class on the wall 9 of the photo space. It looks amazing. I can't wait to place them. I will invite all the neighbors to view them ."
Sid: "Archie is also very happy. OK. I will take some more photos and I will be back in 23 Ms. Oh, by the way, I just put those photos on the db_buffer_cache shelf. The SID directory number is 1332935 ." DEBBIE: "Yes, goodbye ."
To make it easy to manage photos, frames, and logs, he uses a special number to create a directory called the SID directory number. He uses these unique and increasing numbers to track all the photo operations in the house. Sid and Debbie are tired of checking the Sid's directory number. Sid writes the "Sid's directory number" on all the photos, video tapes, and negatives. Finally, they reduced the "Sid directory number" to SCN. Remember SCN, Sid's life revolves around it.
The family now knows that this number is short for SCN. You can see SCN everywhere. Sid writes them on the negative film, and then writes the low and high SCN outside each pack of negative films. Debbie wrote them in the place where she placed the photos. These numbers are particularly important in Sid's complex family life.
Debbie put the photo in the frame. Every frame in the House is of the same size. Some frames only save one photo, while some frames save several photos. Some extremely large photos occupy multiple frames. Sid has a photo of the same size as the original object. He took a shape in the air after skydiving. This photo occupies two frames. When a photo spans a frame, Sid is called a photo chain.
At any time, as long as Debbie changes the photo in the frame, she writes the SCN of the photo on the frame. Each photo in the house has a unique number. They call this number the ID of the photo. These photo IDs help Sid manage all the pictures on the walls in the home. If he needs to find a photo as soon as possible, he can use the photo ID. With the photo ID, Sid can quickly find the wall and the frame for storing the photo.
Sometimes, Sid changes the photo. If he wants to edit a photo, he asks Debbie to find his photo by the photo ID. Debbie gave him a copy of the entire frame containing the desired photo. To prevent Sid from changing his mind and dislike the changes he has made, he puts the copy in a storage room, which is called a "back-to-storage. After Sid is changed and confirmed, Debbie puts the changed photo back to the original place on the wall and writes the new SCN on the frame. If Sid doesn't like his changes, they pull the frame from the "back" Storage and put it back on the wall. In this way, the photo is the same as the SID before.

1.1.3 Logan troubleshooting
Debbie was very busy processing SID photos, so she didn't have enough time and effort to process Sid negatives. Sid thinks that his son has wasted too much time playing video games and eating potato chips. He decided to schedule tasks for them.
Sid's eldest son is Logan William Randolph. Lgwr is printed on the shirt of Logan. Logan has a very simple but important task. The SID camera generates a photo and a negative film. The Logan task is to put the negative film into the notebook. There is another shelf in the kitchen in the house, and the Sid on the shelf is tagged to mark the negatives sent to the eldest son. The label is called "log_buffer". Logan is sitting at the kitchen table and observing this special log_buffer shelf. When a negative film was put on this shelf, he immediately put the negative film in his notebook. Sid calls these laptops "redo their laptops ". He uses this name because he can use the negative film to create a new photo later. Logan checks his shelf more frequently than Debbie. Sid indicates that a new photo can be made at any time as long as there is a negative film. A short and warm conversation between Logan and his father:
Sid: "Logan, the negative film is on the shelf !"
LOGAN: "I will handle it right away ."
Logan puts the negatives into the "redo notebook" in the order they get the negatives ". Once the current notebook is filled with negatives, he will change to another notebook. Every time he changes his "redo notebook", he makes a record on the "alarm notebook" and notifies his brother to do their housework.
Sad, isn't it? Dad and his eldest son are too focused on negatives!
By the way, not all photos have their corresponding negatives. Sid specifies that some photos do not need to be logged, and no corresponding negatives are stored in the redo notebook. Sid calls it "no log ".

1.1.4 events related to Archie
Archibald, the second son of Sid, has another task. His shirt says arch. Archie extracts negatives from the redo notebook and places them in a safe place.
When Archie finds that Logan is switched to another notebook, he starts to operate. He picked up the negatives in his notebook and put them in a safe place outside the house. Sid built a wet-controlled basement in the back yard. That is the safe place for storing negatives. If the storm breaks the house, he can use the negatives stored in the basement to replace the damaged photos. Each copy of Logan's "redo notebook" is called "ARCHIVE redo notebook ".
Maybe one day, you can hear the joke between Sid and another child:
Sid: "Archie? Where are you ?"
ARCHIE: "Dad, I'm in my room. Does Logan switch my notebook now ?"
Sid: "Yes, he just finished ."
ARCHIE: "You know, Dad. I will copy these negatives and create a new notebook in the basement. Then, I will update the 'Control docker' and write a record in the 'alarm docker ."
Sid: "You are a good boy. I know you can trust you ."

1.1.5 Chuck's anecdote
Chuck, the youngest son of Sid, ensures that everything is synchronized. His full name is Charles kenth patrick thomas. The letter on his shirt is ckpt, and Chuck's task is to coordinate the photo numbers on each wall, album, and clipboard with the numbers in the control notebook. As soon as he got the signal, he began to run in the house, write numbers on each wall, and record the same number in the control notebook. This makes everything work together. The following is a conversation between Sid and Chuck:
Sid: "Hi, Chuck ."
CHUCK: "Dad, have Logan started to replace his notebook ?"
Sid: "Yes, son, you know the rules. Run the room with the directory number 1332935 and write the number at the beginning of each wall, the cover of each clipboard, and the top of the photo box ."
CHUCK: "No problem. Just give me a few microseconds ".
Sid: "Don't forget to write 1332935 in the control notebook !"
CHUCK: "Dad, I know. I have done the same thing hundreds of times in a day ."
I bet you're tired of reading this crazy Sid house, aren't you? So far, you may have seen that Sid has an abnormal family. Abnormal functions? Yes! But it is effective and reliable. Sid like this.

1.1.6 control notebook
How does this family maintain all these activities? Sid, Debbie, Logan, Archie, and Chuck determine that to collect and organize the photo well, you must take a lot of detailed notes. Each of them writes their own stuff into a log, which is called "control notebook ".
The control notebook has a home property list entry that records every wall, clipboard, and photo box in the house. If sid adds a room to place more photos, he makes a record in the control notebook. When Logan changes and rewrites his notebook, he makes a summary record in the control notebook. Each time Archie creates an archive redo notebook and puts it in the basement, he writes the name and SCN range in the control notebook. Every time Chuck finishes a lap in the house, he also records the details in his control notebook. This special notebook dynamically stores asset conditions in all locations and processes represented in numbers in the house.

1.1.7 alarm log
From time to time, there will always be some accidents and errors. Debbie may have a problem when placing the photo in the frame, because there is no extra space on the wall. Archie may not be able to fold the negative film because someone sprayed soda on it. Sid, considering all the possibilities, bought a spiral-axis notebook and put it in the kitchen drawer. Write "alarm logs" on the notebook's face ". Every family member writes the problems in this log. They should not only write down the errors, but also write down the normal activities. This alarm log is a convenient place for storing what is already happening in the Sid's home and what is about to happen. If they want to explain the extra details in a specific situation, they make a new "tracking notebook" and record the information in it. In this way, the alarm notebook will not become more messy than it was previously.

1.1.8 early morning program
The family wakes up in the morning and always goes to bed at the same time. These are called "start" and "close" of a day ". The following is the morning Startup Program:
Sid got up from the bed and started his day with a cup of coffee. On the edge of the coffee pot, he saves a series of commands in his notebook, called the initialization parameter file. Read this command to help him start a new day. With coffee in his hand, he walked over to check whether his notebook was placed in the old place. He woke up Debbie, Chuck, Logan, Archie, Simon, and Pamela in the House (you will soon meet them ).
When everyone wakes up, open the control notebook. Make sure that according to the control notebook content, all the photo walls are OK. When everything is checked, he opens the house to greet the guests and starts taking photos. Sid hired a butler, Simon, who helped him in the morning. Simon's tail server wrote the letter SMON (saving a letter from his name ). Some houses are messy in the morning, because every member of the family did not clean up their affairs in time during the previous sleep. When Simon is in place, Sid opens the curtain, hangs the phone, opens the door lock, his family opens, and prepares to greet the guests. Sid and Simon may start the day like this:
SIMON: "Good morning, sir. What can I do for you today ?"
Sid: "Good morning, Simon. It seems that we are very messy here. We suddenly broke down last night. Can you handle all the incomplete photos and 'rollback '."
SIMON: "Of course, all the negatives in the redo notebook will be re-created and placed in a simple order in the right frame ."
Sid: "after you finish processing these items, you can proceed with 'rollback', right ?"
SIMON: "Of course, sir. I pulled the photo frames from the back-to-storage room and put the old versions back to their original places ."
Sid: "That's great. After you finish, I will open the house ."

1.1.9 nighttime Program
The Night Program of Sid's house is also interesting. When Sid lie down and prepares for rest, he asks that everything in the house be put, turned off, and stopped. The first action of bedtime was to ask all the guests in the house to go home. Sid has four mood conditions at night. First, sometimes he is very patient and waits for all the men and women to leave on their own before going to bed. Second, Sid is not patient and he personally monitors every guest, when the guest finishes his/her work (Reading photos and so on), he instructs the guest on his/her way out. Third, Sid is very impatient. He takes the guest to accompany them out, don't let them finish what they are doing. Fourth, Sid pulls the power gate of the house and shouts "time is up". The house is in a mess. Simon had to clean up the chaos the next morning.
When a guest leaves a mess, Sid calls his maids pamelamonica. She monitors guests' activities and handles the aftermath after the guests proceed. Her cleaning device is labeled with pmon.
If sid does not suddenly open the gate, everyone turns on the light and cleans up. Synchronize the notebook to complete their respective tasks. Debbie took all the photos from the db_buffer_cache shelf and put them on the right wall. Logan is correct
The shelf for storing log_buffer is empty, and all negatives are in the current redo notebook. Chuck circled the house and updated the walls and laptops with the highest and lowest directory number (SCN. Archie puts the last negative film in an archived redo notebook and in the basement of the backyard. Then update the control and alarm notebook. When everyone completes, Sid turns off the light and everyone goes to bed.

1.1.10 Sid issue
Sometimes, there may be problems in Sid's house. When any of the following events occurs, the activity in the house stops.
? When the SID wakes up and cannot find the initialization file, it cannot start the day's work.
? Sometimes, Sid needs to use a negative film stored in the basement of the backyard to restore the lost photo. If a negative film is lost, or the negative film is damaged during restoration. He cannot recover any shot after the invalid negative film.
All photos.
? Sid lost several negatives at a time. He accidentally opened the camera and exposed the film. This makes him very bad, and his world seems to have come to an end. He contacted the camera manufacturer and they provided a special camera with two film chambers. In this case, in case of film damage, he can still count on the film in another compartment. Sid is called an image.
? If the basement in the backyard is full, Archie has no space to store new negatives. Archie is just waiting for a new space in the basement. This causes Sid and Debbie to wait, and the Family Activities of the whole Sid are paused.
? If Debbie has the flu, he is in bed. You can guess what will happen: Sid closes the door frantically. Despite these problems and other family setbacks and malfunction, Sid families can still process millions of photos and thousands of simultaneous guests.

Like me, you may want to know How Sid has so much time and energy for photo collection activities. Is he not at work? Actually, no. Money is not the target of Sid. He does not have to work. He made a smart investment a few years ago. He bought a large number of computer companies after 1984, when they were just about to be released to the public. His company is headquartered on the mangrove coast of California.

After introducing the SID family, you will find that it has designed a structure for all the activities of the family. Just like this family activity, Oracle databases also have space, processes, and programs. In my mind, I will briefly describe the Oracle database architecture, processes, and operations that are part of ORACLE data backup and recovery. You may find similarities with sid's.