In this episode of the Oracle University Podcast, Lois Houston and Nikita Abraham explore the intricacies of trail files in Oracle GoldenGate 23ai with Nick Wagner, Senior Director of Product Management. They delve into how trail files store committed operations, preserving the order of transactions and capturing essential metadata. Nick explains that trail files are self-describing, containing database and table definition records, making them easier to work with. The episode also covers trail file management, including the purge trail task and the ability to download trail files directly from the web UI, providing flexibility in various deployment scenarios. Oracle GoldenGate 23ai: Fundamentals: https://mylearn.oracle.com/ou/course/oracle-goldengate-23ai-fundamentals/145884/237273 Oracle University Learning Community: https://education.oracle.com/ou-community LinkedIn: https://www.linkedin.com/showcase/oracle-university/ X: https://x.com/Oracle_Edu Special thanks to Arijit Ghosh, David Wright, Kris-Ann Nansen, Radhika Banka, and the OU Studio Team for helping us create this episode. ------------------------------------------------------------- Podcast 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! 00:25 Nikita: Welcome back to another episode of the Oracle University Podcast! I’m Nikita Abraham, Team Lead of Editorial Services with Oracle University, and I’m joined by Lois Houston, Director of Innovation Programs. Lois: Hi there! In our last episode, we discussed the Replicat process. That was a good introduction, and you should give it a listen if you’re interested in the fundamentals of GoldenGate 23ai. 00:49 Nikita: Nick Wagner, Senior Director of Product Management for Oracle GoldenGate, is back with us today to talk about how to manage Extract Trails and Files. Hi Nick, it’s a pleasure to have you with us. So, we’ve spoken about trail files in our earlier episodes. But can you tell us about the kind of information that’s actually stored in these files? Nick: The trail files contain committed operations only. In an Oracle environment, the extract process is actually able to understand and read both committed and uncommitted transactions. It holds the uncommitted activity and the cache manager associated settings. As a transaction is committed, it's then flushing that information to the trail file. All this information in the transaction is preserved, so we have not only the transaction itself, but the order of the operations within that transaction. All the changed columns, including the primary key and any scheduling columns are also captured, and this is controlled by the log or sub calls parameter and other parameters within the extract process. The data captured depends on settings in the extract file and you can include additional information, including tokens. The trail files also contain metadata information, where the trail files are what we call self-describing, which means that as we start reading in new objects, we start writing the definition of those objects into the trail file themselves. 02:11 Lois: Nick, what does the structure of a trail file look like? Nick: The trail files have a header information, which simply keeps information about what version of trail file this is, where GoldenGate is handling it, information about that trail file itself. You'll also have three different types of records. You'll have a data record, which contains the actual before and after images, the table update statement, the type of operations. You have a database definition record, which includes information about the database that GoldenGate is capturing from, and then you'll also have a table definition record. As GoldenGate starts up and creates a trail file for the first time, it's always going to write the trail file header and associated database definition record, and then it's going to start reading data out of the source database. As it encounters a new table for the first time in that trail file, it's going to write the metadata for that object as well. This makes it very easy. This means that within a single trail file, any data records I have in there, that trail file also contains the associated table definition record for that table. 03:20 Nikita: Let’s talk about compatibility between different versions of GoldenGate. How do the trail files fit into that? Nick: The GoldenGate trail files themselves have information built into them to help understand what they're compatible with as far as GoldenGate releases. If I'm replicating from a new version of GoldenGate to an older version of GoldenGate, I can set the format release value to tell the extract process to write these trail files in an older version. In this case, I can simply say format release 19 and it'll ...
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