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Monday, February 18, 2008

Useful links on Oracle XML DB

Written by Paweł Barut
Here is bunch of useful links related to Oracle XML DB and handling XML data in Oracle PL/SQL. It's mostly for my own reference, but I hope it will be useful for others too.

Cheers Paweł

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Monday, February 11, 2008

CPUJan2008: One thing that every DBA should know about it.

Written by Paweł Barut
While reading documentation for latest Oracle security patch CPUJan2008 for database I've noticed one new required step. This step is: Recompile Views. One whould say that it's nothing strange, but to run this script database have to be started in UPGRADE MODE. For non-RAC installations it's not big issue, as anyway you have to plan downtime. But Oracle suggest that this recompilation can take 30 minutes:
"In one internal Oracle test with approximately 2000 views and 4000 objects, the total execution time for view_recompile_jan2008cpu.sql and utlrp.sql was about 30 minutes."
Practically in my case it took no more than 5 minutes, so it's not big deal.
But it could be problem for RAC installations, that used when CPU is applied on one node, then catcpu.sql is run, then second node is being patched. So normally DB will be all the time available. But if it's needed to start database in UPGRADE mode it means that downtime is required. According to documentation it's not required to run view recompilation script during paching process. This script can be run after,
"however, the CPU installation will not be complete until the view recompilation is completed."
You can ommit this step only if:
  • Databases was created with Release or later

  • Databases was created with any release (for example,,, or after CPUJan2008 or a later CPU has been applied

I hope it also means that after CPUJan2008 was applied you will not have to run this script after next CPU came out (CPUApr2008, etc).

Cheers Paweł

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Sunday, February 03, 2008

Spam, Spam filters, Being Spammer, Being Filtered-out ...

Written by Paweł Barut
My thoughts about Spam. Some time agou I wrote about spam in comments on my blog, but this time it will be about email spam. This is something that from time to time irritates me a lot. Spam is something that nobody wants to see in his mails. And to solve this problem there are many spam filters, IP Block lists and other solutions. But none of them is 100% accurate. And this is what causes problems. Spam filers should be solving problems, but many times creates new ones.
In ideal situation spam filter eliminates 100% of spam, and passes 100% of emails that are expected by users. But it's not true. I will now show example situations, that lead me to conclusion, that spam filter are useless.
Situation 1.
Spam filter did not recognized spam mail, and I have to manually figure out that this is spam. So I need to one more click to delete message.
Situation 2.
Spam filter deletes mail that was intended for me. This was false alarm as it wasn't spam.
Situation 3.
I've send email to customer/friend. His spam filter blocked it. I did not received any delivery failure message.

In my opinion situation 2 and 3 are very dangerous and I would like to avoid any of those situations. In my opinion those situations makes spam filters useless. It is especially dangerous if this block is done by service provider, and when you cannot see list of spam being filtered out. This is what really annoys my and makes me angry. In fact it makes whole email system unreliable (I do not want to say useless), as you never know if you recipient get your email or not.

I do not know what is solution for this. I can see few options, but none of them is perfect:
  1. Each and every email should be signed digitally by sender, and additionally by his service provider. Spam filers should be able to verify this and honor such signing, and not consider this to be spam. Of course spammers could find way to sign theirs mail too, and vanish this approach.
  2. Everybody should use "return receipt" to confirm mail delivery. Well, quite simple, but personally I never allow my mailer to send confirmations, as I do not want to reveal when I've read mail.
  3. Make mail system payable. So for every mail you send you have to pay small amount of money. $0.01 per email should not be problem for real email users, but could cost fortune for spammers. For this money service providers should ensure that your mail will reach recipient.
  4. Use captcha to validate that email is send by real user. I could work as this: when spam filter suspects spam, it sends back email to sender with link to web page on which user will have to provide answer to captcha to make his mail pass throu spam filter.

At the end I would like to ask you: How do you deal with spam?

Cheers Paweł

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