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DB2 12 REORG To Support EasyTier

October 25, 2016

Storage technology keeps improving, which is obviously a good thing. However, DBAs may not always be up to date on these changes and how they impact application performance. (In our defense, we DBAs have a lot on our plates!) I started writing about this two years ago, and followed up by asking the potentially contentious question, “Are REORGs Still Necessary?”

(The reason I say contentious is because many people feel REORGs are absolutely necessary to improve performance on some critical applications. In shops like these, the idea of not running a REORG seems preposterous. Of course I'm aware of people who say they've never run a REORG on a table or index space because of the size. I'm also sure these applications aren't running as efficiently as they could if the table space or index space had been REORGed.)

When I first wrote about it, EasyTier was implemented with the DS8870 storage device. The purpose of EasyTier is to monitor the usage of the datasets. Datasets that aren't read much are moved off to older, slower HDD devices, while those that are read a lot are moved to higher-performance flash SSD drives. The problem I cited was that a REORG would create a new, reorganized copy of the dataset that was meant to be stored on an SSD drive, and store it on the HDD drives. The REORG would also discard everything that was known about the read activity of the table or index space. While over time EasyTier would return the datasets to the SSD drives, this would obviously dramatically impact the performance of critical applications in the short term.

However, with the now available DB2 12, the REORG utility will preserve the activity and keep the new reorganized dataset on the faster flash SSD device. It appears you can now take full advantage of EasyTier and REORG table or index space whenever you need to.

Posted October 25, 2016| Permalink