April 1999
Intermediate to advanced
552 pages
15h 39m
English
Content preview from Oracle Distributed Systems
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Communication Flow
Yourreplicated environment is probably not as simple as a master site and a snapshot site. Oracle allows you to mix and match endless permutations of masters and snapshots. A site can even be a snapshot site for one set of tables and a master site for another. Somehow, all of the data gets to its destination.
The most complex configuration for updateable snapshots is one in which two or more multi-master sites have their own snapshot sites, as shown in Figure 13.1.
Figure 13-1. Updateable snapshots where multi-masters have their own snapshot sites
Suppose that a user at the snapshot site PSLS.BIGWHEEL.COM makes an update to the SALES_LEADS table. How does that change propagate to the updateable snapshot of the same name at site PSFO.BIGWHEEL.COM? The process is as follows:
The user updates the snapshot SALES_LEADS.
The trigger USTRG$_SALES_LEADS creates an entry in the snapshot log USLOG$_SALES_LEADS. (In Oracle8, this trigger is internalized and therefore not visible in the data dictionary.)
The snapshot refresh updates master table in PHQS.BIGWHEEL.COM.
The replication trigger SALES_LEADS$RT in PHQS.BIGWHEEL.COM queues the update for propagation to its companion master, PCAL.BIGWHEEL.COM. (In Oracle8, this trigger is internalized and therefore not visible in the data dictionary.)
When the update is applied at PCAL.BIGWHEEL.COM, the trigger TLOG$_SALES_LEADS creates an ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.