This is the 113^th edition of Log Buffer, the weekly review of database blogs.

Sheeri Cabral gets things going this week with her coverage of this rumour: Monty Widenius Leaves Sun/MySQL. If it turns out to be true, that seems like bad–or at least sad–news for MySQL, but Sheeri’s take is mostly an optimistic one.

MySQL’s Kaj Arno responds to the rumours on Monty resigning: “First, it’s a rumour.  . . .  Second, Monty’s resignation has been a possible outcome already since years before the Sun acquisition.  . . .  I can neither confirm nor deny the rumour.”

On CNET’s The Open Road, Matt Asay says. “Monty has done the right thing with his dissent. He has taken it outside the company, as Arjen Lentz, MySQL’s twenty-fifth employee, did before him. Arjen continues to be both a promoter and critic of MySQL, but is able to do so publicly without the constraints of an employee agreement. I assume Monty will do the same, and rightly so.” That’s not all the response out there, and there will certainly be still more as this develops.

In non-Monty blogs, Brook Johnson of Database Science asks, can a timestamp be slower than a datetime? (more…)

In an Oracle-l thread, this question was raised: how can you find objects creating nologging changes?

First, what is a ‘nologging’ change?

The redo logging mechanism plays critical role in media recovery. Media recovery relies on archivelog files generated to roll the database forward. A standby database or dataguard recovery also relies on archivelog files. It is possible to do DML changes with minimal logging, i.e., nologging changes, also known as direct mode inserts. For example, insert /*+ append */ can be used to populate the rows into a table without generating much redo. This can invalidate the standby database and might trigger rebuilding some or all parts of the standby database.

nologging changes generates minimal redo, since the blocks are pre-formatted and written to disk directly. A redo record is generated, invalidating a range of affected blocks. This invalidation redo record size is far smaller, for e.g. hundreds of blocks can be invalidated using just a single redo record. Of course, recovery is severely affected as the changes performed with nologging operations cannot be reapplied/recovered.

Internals of nologging changes

Since nologging is all about redo records, dumping the redo log file or archivelog file is a concrete way to see what happens under the hood. Let’s consider an example to explain the internals of nologging changes. We will create a table, insert rows, and closely review the redo records.

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Almost everyone and their mum has been twittering about (or from) Mozilla Labs’ newest creation, Ubiquity. You can get a quick introduction of this firefox extension via their blog post, which has a video tour.

Well, after playing around with the simple stock commands (email, wikipedia search, twittering), I decided it was time for a handy Oracle search function. I emerged from my cave with a pretty basic Ubiquity command that will search the tahiti documentation, and optionally search the documentation for a specific version of Oracle from 9iR2 onward. Right now it will simply take you to the Oracle search results page. If I find that Oracle is providing an API to the tahiti search engine, I may enhance it to include results in the Ubiquity preview pane.
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Some of you might know that for more than two years we have had an office in Sydney, Australia. Last year, I had the pleasure to travel there to present at the AUSOUG conference and work from our office in Sydney. It’s been a huge pleasure, especially if you consider what was going on back in Ottawa at that time.

Long story short — I’m moving to Australia. My flight from Ottawa leaves in three hours and I’m all packed and ready to go. Today we had a kiss-goodbye lunch at here at the Pythian office in Ottawa, and I was presented my new role Down Under. Hmm . . .  to be honest, I expected it to be somewhat different:

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Welcome to the 112^th edition of Log Buffer, the weekly review of database blogs.

First, thanks to last issue’s contributors–Joe Izenman, Dan Norris, and Jason Massie–for snatching victory from the jaws of defeat and making LB#111 a worthwhile read. That’s what it’s all about!

Oracle’s up first, starting with our old friend Doug Burns and his Time Matters series, in which he holds up to the light the concept of DB Time: “. . . [the] total time spent by user processes either actively working or actively waiting in a database call.” He continues, “There’s a lot more I could say about DB Time. Like all of the best performance concepts or methods (e.g. YAPP, Method-R) it can seem so obvious as to not be worth saying, but contains an enormous amount of common sense and technical rigour.”

Arup Nanda writes about the time he spent Diagnosing Library Cache Latch Contention. About half an hour, as it happened, but he’s a real pro, and his analysis just goes to show. To quote, Nuno Souto–who makes the best blog endorsements– “Damn useful stuff . . .  bookmarked.”

Tanel Poder has another script for you to fall in love with, which makes its debut in flexible sampling of any V$ or X$ view with sample.sql. It is, writes Tanel, “ . . . a simple but powerful sqlplus script for ad-hoc sampling of any V$ view.”

Kenneth Downs, the Database Programmer, offers Advanced Algorithm: Sequencing Dependencies, a smart look at satisfying dependencies in databases. What does that mean? Well for example, Kenneth writes, “All popular Linux distributions have a package installation system in which each package lists its required dependencies. If you want to install a large number of packages in one shot, producing a tangled bunch of related dependencies, today’s algorithm can be used to work them all out.”

That’s the kind of task for which we humans use tools like mind maps. Jason Arneil shares his ASM Mind Map.

Laurent Schneider went off-road and came back something not on the map at all: the difference between rollbac and rollback.

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The process of adding a node to a 11.1 RAC is very similar to the 10.2 process described in Part 5 of this series. For this reason, this post will just focus on what has changed between the 2 versions. Here is the complete series up to now:

1. Installation of 10.2 And 11.1 Databases
2. Patches of 10.2 And 11.1 databases
3. Cloning Software and databases
4. Install a 10.2 RAC Database
5. Add a Node to a 10.2 RAC database
6. Remove a Node from a 10.2 RAC database
7. Install a 11.1 RAC Database
8. Add a Node to a 11.1 RAC database (This post!)
9. Remove a Node from a 11.1 RAC database
10. A ton of other stuff you should know

Before you start

Make sure you’ve kept a copy of the voting disk and that you have a backup of the OCR. Check that the locations for all the components to be installed, i.e.: Inventory, Clusterware, ASM, database software, OCR, Voting Disks, and data files, are writable. Confirm that all the prerequisites are met for the node and for the whole cluster with the node to be added.

Refer to the Oracle Clusterware Administration and Deployment Guide
11g Release 1 (11.1) - 4 Adding and Deleting Oracle Clusterware Homes
and the Oracle Real Application Clusters Administration and Deployment Guide
11g Release 1 (11.1) - 9 Adding and Deleting Oracle RAC from Nodes on Linux and UNIX Systems for the complete reference of how to perform these steps.

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Crisis has struck! This week’s Log Buffer editor had to beg off at the eleventh hour when his time vanished. It happens. But, in every crisis, an opportunity (well . . .  maybe, maybe not). The opportunity — an open discussion of this week’s best database blog articles. Readers in control.

Log Buffer is always looking for editors, so if you’d like to step forward and publish one on your own blog, read the Log Buffer guidelines and send me an email.

I’m going to go through my bookmarks and add my own presently. I hope to hear from you!

Anybody who has tried this multi-node to single-node cloning in 11i knows that it’s difficult and very error-prone. If we outline the Apps Tier cloning process, it looks like this (supposing we have a two-node instance with the DB and CM on one node, and Web and Forms on the other):

# CM Node
# copy all files to the target
$ perl adpreclone.pl appsTier merge

# Web Node
# copy $COMMON_TOP/clone/appl directory only to the target
$ perl adpreclone.pl appltop merge

# Target Node
$ perl adcfgclone.pl appsTier

This process is called merging appltops. It’s not as easy as it looks. Many times, the production environment might not have proper values in the fnd_nodes table, which makes adcfgclone.pl fail to properly recognize the appltops for merging.

But in R12, life is made easy. (more…)

Just a quick post to get myself back into blogging mode. Recently in IRC (#oracle on freenode, to be precise), a fresh face asked if the Block Change Tracking file ever shrinks. She had been worrying about the file in her instance continuing to grow. A number of us speculated (non-BAAG!) that perhaps taking an RMAN backup would somehow purge the file of what it was keeping track of, and then the magical Oracle fairies would promptly resize it for us. Needless to say, I was hesitant to take this theory forward with Alex Gorbachev aware of my home address.

After setting up Oracle 10.2.0.1 on a nice VirtualBox image
(more on that in another post) running CentOS 5, I began to do some reading. For some reason, actually reading the official tahiti docs was last on my list. A search of the 10gR2 docs quickly yielded this (from RMAN Incremental Backups):

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A few days ago I had a new idea for a blog post. A post about what it really takes to be a good database administrator. I began by researching what others had done on the topic. At the end of this post you will find links to six of the posts I found that provided some insight into this question. Even after uncovering this information, I thought I could add something to the mix from my own experiences. So here we go!

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