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Slow Excel link report performance caused by 'Cost Threshold of Parallelism' setting

Troubleshooting


Problem

User opens an Excel link report (XLSX file). User presses F9 (to run/refresh the report). This takes a long time.

Symptom

Example:

In one real-life customer example:

  • Cost of Parallelism = 50 => large/complex report took was not finished after over an hour (after which time the user gave up waiting)
  • Cost of Parallelism = 5 => large/complex report finished after 26 minutes.

Cause

There are many possible causes for slow Excel link report speed.

  • TIP: See separate IBM Technote #1347497 for more examples.

 

This Technote specifically relates to the scenario where the slowness is caused by the SQL setting 'Cost Threshold of Parallelism'.

 

More Information:

By default, the Microsoft setting 'Cost Threshold of Parallelism' is configured to be 5. If this value is modified, it can cause unexpected performance issues.

Environment

Controller database hosted on Microsoft SQL server.

Diagnosing The Problem

To check/view the current setting/value of Cost Threshold of Parallelism:

1. Launch SQL Management Studio

2. Right-click on the server name, and choose 'Properties'

3. Click on section 'Advanced'

4. View the settings inside section 'Parallelism':

image-20181219150629-1

Resolving The Problem

Modify the setting for 'Cost Threshold of Parallelism'.

 

Example:

In one real-life customer example:

  • Cost of Parallelism = 50 => large/complex report took was not finished after over an hour (after which time the user gave up waiting)
  • Cost of Parallelism = 5 => large/complex report finished after 26 minutes.

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Document Information

Modified date:
19 December 2018

UID

ibm10792025