Tuesday, December 29, 2009

A Case Against "New and Improved"

My email provider has recently switched their webmail interface from a straight HTML version to an Adobe Flash based version. I don't really use this version a lot since I use Thunderbird as an email client, but it has some nice new features that I guess are helpful if you use the web interface a lot.

I was recently on vacation bouncing between four different hotels without a laptop. I came to appreciate the straight HTML interface more as I moved from place to place. All of the hotels I visited had "business centers" or public computers that you could access (some free, some not). I ran into two major problems with these computers; you can't install an updated version of Flash on a computer where you are only a guest, and Flash operates really slow over satellite connections.

I felt a bit of deja vu as I remembered the transition from Client/Server based programs to three-tier architectures in the earlier part of the decade. Here we are again with a thick version specific client. The more things change, the more they stay the same.

Saturday, November 28, 2009

New to the "Top 5" list

A new entry to my all-time Top 5 list of bad advice I got from Oracle Support:

Oracle Support: You should distribute your log groups to multiple disks to avoid contention.
Me: But doesn't Oracle write to only one group at a time?
Oracle Support: No, we're multi-threaded.
Me: So you're telling me that Oracle writes to more than one redo log group at a time?
Oracle Support: Yes.
Me: Please close this TAR, I'll open another one.

Wednesday, October 28, 2009

Virus'

I've been battling the "Vundo" virus on a machine I was asked to work on for a family member. Somewhere between the 13th and 14th time scanning with Trend Micro's Internet Security, my mind began to wander.

Exactly what type of person writes a virus intent on inflicting aggravation on countless people? Are virus programmers the same people that cut you off in traffic? Are they the type of people that beat puppies?

I bet there are plenty of virus writers who think it's funny when a bus blows up.

I finally came to the conclusion that these people are lower than dog shit. I hope they can carry on a conversation with Saddam Hussein when they meet him.

Friday, September 04, 2009

Pick Two

There's a saying in the computer business, "Good, Fast, Cheap. Pick Two." This saying represents the trade offs we have to make every day on the front lines of IT.

Recently, we have started playing around with MySQL Enterprise Monitor (MEM). MEM is MySQL's offering for an event driven monitoring application similar to Oracle's Enterprise Manager. There are four pieces to MEM; the monitoring agent that gathers that db statistics, the query analyzer that allows you to "trace" queries, the connection proxy that allows you to redirect connections, and the data repository.

Our first stab at configuring MEM was putting the monitoring agent, query analyzer, and query proxy on the host being monitored with the repository db on a different machine. This actually worked pretty well until we had some big queries run through the query proxy. CPU utilization spiked because both the query proxy and the database had to handle the same set of data.

So MySQL Support suggested we move the proxy, query analyzer, and monitoring agent to a separate host. This "middle-tier" would handle the extra CPU load we were generating and keep our db host performance consistent. This solution worked very well, except we weren't getting host related statistics like CPU utilization on the DB host.

No problem, right? We moved the monitoring agent to the db host and kept the proxy and query analyzer on the middle-tier. Now we had our host related statistics, except we couldn't get the query analyzer to work because it has to have a monitoring agent present in order to work properly.

The only solution MySQL Support can offer us at this point is to have two agents monitoring the same database; one on the middle-tier host and one on the db host. OK, we'll do what needs to be done, but I have two fundamental problems with that configuration. First, my database background tells me that duplication will come back and bite you in the ass someday. My other very practical issue is now we are storing twice as much data in the repository for 10% more information.

So while the concept of MEM is great, the actual implementation is a compromise.

Note: Some of the above configurations are not currently supported by MySQL. Use at your own risk.

Monday, August 17, 2009

SGA Latch Contention

We had been getting a pretty persistent "WARNING: inbound connection timed out (ORA-3136)" error thrown to the alert.log on one of our 10.2.0.4 dbs. This error wasn't received once or twice, but about 40 times within a 2 minute window.

I did the research on it and found some sources that suggested my SQLNET.INBOUND_CONNECT_TIMEOUT needed to be adjusted upwards from the default value of 60 to 120 or something higher. I was pretty sure that wasn't the case as it was already set at 120. For the sake of progress, I bumped the timeout to 300 (5 minutes) and monitored closely.

About two days later, we received the same warning message in the alert.log file, except this time it happened about 90 times in a two minute period. Aha, a change. So that told me that something was going wrong during the authentication phase since increasing the connection timeout made the problem worse.

During the last occurrence, I also noticed that the mman process was consuming 100% of the CPU. At the time I wasn't sure if it was a symptom or a byproduct of the problem. However, as soon as the problem went away, the ora_mman process went back down to nearly 0%.

I setup a script to automatically do three systemstate dumps a minute apart when the mman process went to 100%. Oracle Support was able to tell me that during this time period, a bunch of my SQL had been invalidated as was waiting on a latch to be loaded back into the shared_pool. They also indicated that this massive amount of reparsing could happen because somebody did a DDL on a popular object or somebody flushed the shared pool.

I was pretty sure nobody flushed the shared pool, but that got me to thinking what would happen if Oracle shrank my shared pool due to the automatic memory management? I checked v$sga_resize_ops and found that around the times of my warning message, the shared_pool was being re-sized down in size. I brought this up to the support analyst and he suggested I set the shared_pool to the maximum size Oracle had re-sized it to.

That was three days ago, and we haven't had a warning since.

The theory is that while the shared_pool was being re-sized in the SGA, Oracle grabbed a latch. The memory resize operation took a while and while Oracle held that latch, nobody could login. Interesting theory, we'll see if it holds.

Thursday, August 06, 2009

PC Support for Oracle

So I'm working with Oracle Support on an Oracle Applications R12 issue. They want to see some data from one of our tables and give me a query to run. I run the query in SQL Developer and export the results as a .csv file and upload it to the TAR.

Three days later they get back to me and say they can't open the files. Hmm, that's funny, let me try the same thing.

I load it into Open Office in about 2 seconds, no problem.

Then I load it into a database using SQL*Loader with no issues.

Same thing with MySQL and LOAD DATA, no issues.

I mail the file to myself and again it works no problem.

I send the file to a collegue and Open Office works for them as well.

The support analyst asks for a plain .xls worksheet so I try to load it into MS Excel. Bingo, I get an error:

This error is usually encountered when an attempt to open a file with more than 65,536 rows or 256 columns is made. Excel is limited to 65,536 rows of data and 256 columns per worksheet. You can have many worksheets with this number of rows and columns, but they are usually capable of fitting into one workbook (file). The number of worksheets you can have per workbook is limited only by the amount of available memory your system has. By default, Excel can manage 3 worksheets, more if there is available memory to support the quantity of data.

Truncation of rows or columns in excess of the limit is automatic and is not configurable. This issue can usually be remedied by opening the source file with a text editor, such as Microsoft Office Word, and then saving the file off into multiple files with row or column counts within the limits of an Excel worksheet. These files can then be opened or imported into Excel worksheets.

If you are using a data format that does not support use of a text editor, it may be easier to import the data into Microsoft Office Access and then use the export feature of Access to import the data to an Excel format. Other methods of importing large source material into multiple worksheets are available, but may be more complex than using either a text editor or Access.

Aha! MS Excel can't handle anything with over 256 columns of data and my data is 325 columns! (Not my design, it comes from Oracle Applications).

I post my findings to the TAR and suggest they load the data into a piece of software that can handle 325 columns, like maybe Oracle. (I didn't have the heart to suggest MySQL, but I guess they wouldn't take that as a slight anymore ...)

Saturday, May 30, 2009

information_schema.tables.table_rows

Here's something to be aware of. The table_rows column in the information_schema.tables table does not accurately reflect the number of rows in the actual table.

This weekend I was moving a db from one host to another. As a good DBA, I took the row counts from each table I was moving so I could check it on the other side. When the copy was done, I queried information_schema.tables again and dumped the results to a file. Running the two files through diff, I found that almost every table had a different number of rows.

I knew that couldn't be possible because I used a method where nobody had access to these tables when I was doing the copy.

On serverA, the information_schema reported that table1 had 2337 rows. On serverB, the information_schema reported that table1 had 2341 rows after the move. Doing a "SELECT count(*) FROM table1" yeilded 2343 rows on both serverA and serverB.

Sunday, May 03, 2009

Some Helpful Drupal Resources

The best resource for understanding how Drupal works is actually the handbooks at Drupal.org.

Learn By The Drop has some very interesting videos about setting up Drupal and some other basic info to get your site up and working quickly. I browsed their screencast about setting up FCKEditor and was very impressed.

There are also some very interesting screencasts at DrupalTherapy.com. In fact, I used the Date + Calendar screencast to setup my own event content type.

Lastly, a blog aggregator called PlanetDrupal is also fun to keep up with.

What are some of your favorite Drupal resources?

Friday, March 20, 2009

SQL Developer Connecting to MySQL

We introduced Oracle SQL Developer to our developers about a year ago. They seem to like it for querying Oracle, but the MySQL connectivity was quirky in previous releases.

Now that Oracle SQL Developer 1.5.4 has been released, I figured I'd give it a try again. I downloaded the software and it started right away with no problem (although I wasn't paying attention and I forgot to migrate over my settings).

Once the software starts, go to Tools > Preferences > Database > Third Party JDBC Drivers and choose the appropriate JAR file.

Then I added a connection with the correct parameters and Voila! I was querying MySQL data from an Oracle tool!

Monday, March 02, 2009

My Oracle Support

Did everybody get the notice that the HTML version of MetaLink is going away?

If you've got a hot duo2 box and your IT Department allows you to install Flash, you've probably already been experimenting with the new version. I tried using it when it first came out but it was so slow on my 2.2Ghz Laptop with only 512Mb of RAM that I had to go back to "MetaLink Classic".

Well, now I have no choice now that my days are numbered. I've got to figure out how to tell my IT group that all my people need new computers because Oracle upgraded their website. Maybe the government can bail us out?

Thursday, February 12, 2009

Point & Click DBAs

Maybe I'm old school.

Maybe I'm just behind the times.

Today's crop of DBA candidates sure know how to point and click their way through Oracle. When I ask them how to tune a SQL statement they'll give me the exact instructions on how to click on some Grid Control adviser or how to get an "explain plan" through TOAD. I guess the new query plan is called "explain plan" now because it's easier to understand.

Recently I asked one candidate, "What if grid control goes away, how do you tune a query?"

"Well, first you start the grid control agent, and..."

"No, no, I mean, if there was no such thing as grid control, how would you tune a query?"

Crickets....

"Um, SQL*Plus?"

Yes, good old SQL*Plus.

I used to believe that GUIs are icing on the cake and as long as you know what was going on under the covers, it was perfectly acceptable to use a GUI.

Maybe I'm just old school.

Tuesday, January 27, 2009

Vista VPN Vacillation

I tried setting up the NCO Secure Entry Client on Vista x64, but just couldn't get it to work. Before I found that VPN Software, I contacted Dell and they sent me out a Vista x32 installation CD that I could use to re-install my OS if it came to that. I messed around with x64 and NCO Secure Entry Client until the install disk came and then I punted. The Vista install took about an hour or so and the VPN setup took another five minutes to setup and test. It came up fine the very first time.

Maybe Cisco will get with the program by the time I'm ready to get a new machine. I wonder if that extra 2G of RAM will fit in my W2K box...

Thursday, January 22, 2009

When the Latest and Greatest isn't the Greatest

I thought my Windows 2000 computer was starting to show it's age. 512M of RAM and a 200G hard drive just doesn't go as far as it used to. I setup a Vista laptop a few months ago and it's working pretty good, so figured I'd take the plunge and get 6GB of RAM and get Vista x64 to take full advantage of it. Everything was going fine (with the normal Vista quirks, of course) until I tried to install the Cisco VPN client. Seems as though there is no support for Vista64 and my particular VPN software.

Dandy.

I found NCO Secure Entry Client and will try to set it up, but we'll see...

Tuesday, January 13, 2009

Adobe Automation

I have a friend who needs some Adobe Acrobat automation. The project description is:
We need to find a programmer who is willing to do some high-end Adobe form work for us.

We need to embed a "send to" button in some of our company forms so we can email the form to clients who can input the data and submit the form back to us by clicking on a submit button on the form.

If anybody has this skill set and is interested, please email me at marist89 (at) excite %dot% com and I will forward to the appropriate party.