Radim Kolar's Blog (35)

Opensource databases such as MySQL and PostgreSQL supports non standard SELECT extension for limiting number of returned rows from query. You can see description in PostgreSQL manual. Look for keywords LIMIT and OFFSET. LIMIT specifies the maximum number of rows to return, while OFFSET specifies the number of rows to skip before starting to return…

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Another DB2 upgrade mini-guide. I was asked to upgrade DB2 Express 9.5.4 to DB2 Express 9.7. Reason for this was that old DB2 Express 9.5.4 was 90-day demo version and demo key expired. Upgrading DB2 will generate new 90-day key and allows to use DB2 for some more time which would be enough for finishing application development. It was small VMware DB2 instance with 1GB ram for using during application development.

I pointed that installation of DB2 Express C will be better because it…

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During searching for some good case studies about deployment DB2 compression in data warehouse environments, Google find

following document on Oracle website. It is description how compression works in Oracle 11g.



While this document have some minor errors inside (for example Gzip does not use block compression) i was quite surprised by presented Oracle compression ratio claimed. I could not… Continue

Few weeks ago IBM did Virtual Experice version of IOD 2009 Las Vegas conference. Using web technologies you can join virtual conference and listen to sessions (more than 30 available), download presentations, chat and mail with other online people (usually 2-5 people around, nice opportunity to find new potential customer) . Its really nicely done and you should take a look and spend there few hours. Its time good spent.

You can register (free)…

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Yesterday, DB2 Express C 9.7.1 was released. I have one non root db2 9.7.0 copy floating around and wanted to update it. Non root db2 installations are very convenient for casual testing. They can be installed quickly by regular user and you do not need to seek assistance of unix administrator.

Updating DB2 Express C linux installations with standard db2 install program is not possible - you have to do reinstall because unix db2 installer do not have ability to do updates like ms…

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Licensing for DB2 Express C changed in 9.7 version a bit. DB2 Express C is still free to use and distribute, but DB2 Express C FTL - Fixed Term License is no more. FTL licensing option was moved to regular DB2 Express Edition.

This is good move because people sometimes criticised that DB2 Express FTL have more issues than regular express version. Also it will make easier sw maintenance for IBM because they can now concentrate on 3 DB2 Editions (Express, Workgroup, Enterprise). DB2…

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IBM Information Management released long awaited Fixpack for DB2 9.7 also known as Cobra. This fixpack comes with

really impressive list of fixes. This list of fixes is not complete list of fixes included in fixpak. IBM, as usual, omits some included fixes from being listed. This is really annoying because our and customers DBA can not easily check (without running their testcases) if their… Continue

Apache Derby is very often used opensource Java database. It is also known as Cloudscape or JavaDB. There are several branches available, but 10.3 is most used Derby branch today. It can be found in Websphere 7, Rational Software Team Concert/Foundation, Websphere CE 2.1 and probably in many many others. 10.1 and 10.2 branches are considered obsolete and 10.4 and 10.5 are considered too…

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Rational Team released 2.0.0.1 version of their Rational Team Concert software. There is some excitement about this version because its not only first bugfix version in shining new 2.0 RTC line, but there are also important licensing changes:

1. It can be freely used up to 10 users (was 3 before)
2. You can now use any supported database engine (was DerbyDB only)

These important changes makes Rational…

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I am amazed how fast is DB2 version 9.7 moving into production. It is much faster then 9.5. I started to see first signs of 9.5 used in production for about 1 year after release.

DB2 9.7 is entirely different. Its already used, deployed on testing systems and used as standard version for new projects. Its pretty good success because there is not even single fixpak for v9.7 out. Fixpak 1 is awaited because it will add Oracle compatibility to DB2 Express Edition, which is very…

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People are changing database backends for their applications for various reasons. I was interested about current trends in database migrations. I used google to search how much documents can be found to particular database migration direction.



i tried mysql first to see if google can return relevant data:

migration "from mysql" 63 700 documents found

migration "to mysql" 242 000 documents found



That was pretty much expected result because mysql is highly popular… Continue

I found interesting blog post comparing speeds of free databases. Test used MS SQL Express (2 versions) and MySQL. I decided to port that test into IBM DB2 9.7 and test it on similar hardware. Original test used CPU Intel Core 2 1.80 GHz, 2 GB RAM, OS: MS Windows XP. My configuration is same except slightly faster CPU running on 2.2 Ghz. I executed only bechmark for DB2 Express C and PostgreSQL, results… Continue

This blog post was initially intended to be part of this thread on DB2 Express C forum but because my blog gets recently included in Planet DB2 blog aggregator i decided to make blog post instead.



I hear on… Continue

We migrated warehouse to DB2 9.7, because we heard lot of success stories related to DB2 9.7 compression. I was quite sceptic about it first, but after hearing more reports we finally decided to migrate too (from DB2 v8).

Data compression

We experimented a bit with partitioning tables (not DPF) and how partition size affects compression ratio. Answer is simple - larger partition size is better. Compression ratio increased slowly until it reached its maximum at about… Continue

Many times people ask me if DB2 will be fast enough for their application. They are usually most worried about INSERT performance. Often acceptable performance means ability to insert 1k rows per second. Can DB2 do that?



To get decent insert performance from DB2 you must turn autocommit off and use prepared statement. This is pretty simple to do and DB2 can insert that way about 5k rows per second into moderate sized (about 1GB) table. Its slightly faster (7k rows per… Continue