Oracle AI in Fusion Cloud Human Capital Management

Lois Houston and Nikita Abraham continue their deep dive into Oracle Database 23ai backup and recovery strategies with Senior Principal Database & MySQL Instructor Bill Millar. Picking up from Part 1, they explore critical concepts such as instance recovery, checkpoint processes, and the role of redo log files. Bill shares insights into complete and incomplete recovery, flashback technologies, and lots more. Oracle MyLearn: https://mylearn.oracle.com/ou/course/oracle-database-23ai-backup-and-recovery/141127/ Oracle University Learning Community: https://education.oracle.com/ou-community LinkedIn: https://www.linkedin.com/showcase/oracle-university/ Twitter: https://twitter.com/Oracle_Edu Special thanks to Arijit Ghosh, David Wright, Radhika Banka, and the OU Studio Team for helping us create this episode. -------------------------------------------------------- Episode Transcript:

00:00

Welcome to the Oracle University Podcast, the first stop on your cloud journey. During this series of informative podcasts, we’ll bring you foundational training on the most popular Oracle technologies. Let’s get started! 00:26

Nikita: Welcome back to the Oracle University Podcast! I’m Nikita Abraham, Team Lead of Editorial Services with Oracle University, and with me is Lois Houston, Director of Innovation Programs.

Lois: Hi everyone! Last week, we had a fantastic chat with Bill Millar, our Senior Principal Database & MySQL Instructor. We dug into the basics of backup and recovery. We touched on everything from a DBA’s role in preventing data loss to handling different types of failures, and even some common mistakes that tend to pop up when managing a database.

Nikita: Yeah, if you missed that episode, definitely go back and check it out. It’s packed with useful info, especially if you’re in charge of keeping databases safe.

01:10

Lois: Today, we’re picking up where we left off. We’re going to ask Bill about instance recovery and recovery strategies. Bill, can you kick things off by explaining what instance recovery is?

Bill: You can understand instant recovery by becoming familiar with the checkpoint process, the redo log files, and the role of the log writer with the redo log files.

Automatically instance or crash recovery. What is it doing? What are the phases of instance recovery? How we possibly can tune that instance recovery. We can use the mean time to recovery advisor that can help us determine how we might tune the instance recovery.

01:51

Nikita: OK, so let’s go through some of these concepts and procedures you mentioned. What is the checkpoint process responsible for exactly?

Bill: The checkpoint process itself, it's responsible for updating the data file headers with checkpoint information. When a checkpoint is taken, it is going to write into the controlfiles. It tells the DB writer to write. DB writer writes to the data files, and the checkpoint is also annotated in the data files.

So updating controlfiles with that checkpoint information also, controlfiles and database files. It signals that DB writer at full check points again, hey, it's time to write. So that way, it has the latest data written to the data files. The controlfile and datafiles, those are in sync with that.

02:40

Lois: Bill, what about the log writer process and the redo log files?

Bill: With the log writer process and the redo log files, the redo log files record the changes to the database himself. It should be multiplexed.

02:53

Nikita: What do you mean by that?

Bill: More than one redo log group. Now, the redo log groups, it is recommended that they should be multiplexed. Each group member should be on a different disk or in a different disk group if you're using ASM.

03:10

Nikita: And why is that, Bill?

Bill: Because if I lose one, if I lose one redo log group, one member, I can continue to operate with just the one. If I only have one redo log group member and the system comes around and tries to write to it, then my system is going to come to a halt.

So the log writer is going to write to those redo logs whenever somebody does a commit. When that redo log buffer is 1/3 full or every three seconds and before DB writer writes. So those are the four mechanism that tells log writer to write from that log buffer to the redo log files. And it'll also write, when we do a shut down, all the buffers will be flush...