Fake Statistics In Catalog May Get Reset By Automatic Update Of Nickname Statistics Feature

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Abstract

You may have been faking the statistics information (e.g. cardinality) for nicknames to influence Optimizer to generate a specific plan. However, please note that, you might see that the plan generated by Optimizer gets changed when you enable the Automatic update of nickname statistics feature or migrate to Federation Server V9.5 with default setting. It in fact results in the fake statistics getting reset by the automatic feature.

Content

When the Automatic update of nickname statistics feature is enabled, the NNSTAT stored procedure will be run automatically, and set new values in statistics catalog tables. Since this feature is enabled by default in Federation Server V9.5, you may see it happens when migrating to this release. Please refer to Information Center for how to disable or customize this feature.

Related information

Information Center Documentation For Automatic update

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Document information


More support for:

InfoSphere Federation Server
Migration

Software version:

9.5

Operating system(s):

AIX, HP-UX, Linux, Linux Red Hat - zSeries, Linux SUSE - zSeries, OS/400, Solaris, Windows, i5/OS

Software edition:

All Editions

Reference #:

1376334

Modified date:

2011-12-09

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