Desktop security: Application data got blurred

Bart Sjerps General

In the old days, when I started messing around with computers for fun as a young geek guy, computer security was pretty simple.

Amiga 2000
Amiga 2000

In those times we were using 8 or 16-bit PC’s with MS-DOS (for the poor guys) or, for the wealthy like myself, Commodore Amiga or comparable computers with real magic inside (who else around 1988 had 4-channel 8-bit stereo sound, 4096 colors, coprocessors for audio and graphics, true multitasking, a mouse-driven GUI handling multiple screens and windows, capable or running a word processor, graphics editor, sound tracker and some other stuff, all at the same time in 512 KB RAM?) (more…)

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Duplexing Oracle Redo logs?

Bart Sjerps FAQ, Oracle, Performance

A customer asked me recently what EMC’s advice is regarding duplexing Oracle redo logs. There is a thought behind this – Oracle redo logs are sensitive to data corruption – if redo logs are corrupt, there is no way to nicely recover the database to a technically consistent state (at least not without restoring data from backups).

This is what Oracle tells you:

Oracle recommends that you multiplex your redo log files; the loss of the log file information can be catastrophic if a recovery operation is required.

 

Duplexed Redo
Duplexed Redo

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Pinpointing I/O bottlenecks on Linux

Bart Sjerps FAQ, Oracle, Performance

Does this story sound familiar?

The end users of a database application start complaining about poor system response and long running batch jobs. The DBA team starts investigating the problem. DBA’s look at their database tools such as Enterprise Manager, Automatic Workload Repository (AWR) reports, etc. They find that storage I/O response times are too high (such as an average of 50 milliseconds or more) and involve the storage team to resolve it.

The storage guys, in turn, look at their tooling – in case of EMC this could be Navisphere Analyzer, Symmetrix Performance Analyzer (SPA) or similar tools. They find completely normal response times – less than 10 milliseconds average.

The users still complain but the storage and database administrators point to each other to resolve the problem. There is no real progress in solving the problem though.

Two Way Communications

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How to set disk alignment in Linux

Bart Sjerps FAQ, Oracle, Performance

As you might know, if disk partitions containing Oracle datafiles are not aligned with the underlying storage system, then some I/O’s can suffer from some overhead as they are effectively translated in two I/O’s.

If you want more info, google for “EMC disk alignment” and you’ll find plenty of information, explaining the issue.

Update 28-03-2013: I wrote a follow-up for this post describing the same thing for Linux (Red Hat / CentOS / OEL) versions 6. For that, you might want to jump straight to the new post as this one gets a bit outdated 😉
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