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In Database Configuration Properties, why does the value 3 for "bi threshold" have no effect?

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TitleIn Database Configuration Properties, why does the value 3 for "bi threshold" have no effect?
URL NameP55020
Article Number000147781
EnvironmentProduct: OpenEdge
Version: 10.2B, 11.x
OS: All supported platforms
Question/Problem Description
Why the default bi threshold value of "3" shown in the Database Configuration Properties view has no effect?
How to un-set bistall limits against a database managed by the AdminServer?
What is the unit for "bi threshold" shown for managed database startup parameters ?
Steps to Reproduce
Clarifying Information
Error Message
Defect/Enhancement Number
Cause
Resolution
For databases managed by the AdminServer, the Configuration Properties view shows default values for database startup parameters. The following Article documents these: This Article uses the bi threshold value as an example and outlines:
  1. While the initial property value shown may be confusing, it is not the AdminServer that dictates default values for unused startup parameters but the database manager.
  2. When a managed database is started, the AdminServer only provides the values for startup parameters that are configured as seen in the Configuration Properties view and recorded in the conmgr.properties file
  3. How to unset a startup parameter in order to revert to the default value for a managed database

Configuration Properties: bi threshold value of 3 MB.

  • This does not set the -bithold against the database when started or write the property to the conmgr.properties.
  • While incorrect, this is an initial field display value only and has no effect on the true default value used when the database is started and shared-memory is initialised with required parameter values. The bi file will grow without size limits to any size within largefile/OS limits despite the Configuration Properties value
  • Any startup parameter that is not present for the managed database in the conmgr.properties file are initialised with their default or calculated value by the Database Manager when shared-memory is initialised, not the AdminServer 
It is only when this initial field display value is changed in the OpenEdge Console Database Configuration view, that the 'bi threshold' startup parameter is then set to the value entered, limiting the size of the bi files to the -bithold value (in Mega Bytes):
          
          OEE/OEM Console:
Databases > dbname > Configurations > defaultConfiguration:
Background Writers - Before image threshold (-bithold)

Once the default value of "3" for the Before image threshold startup parameter is changed in the database Configuration view, it is written to the conmgr.properties and used when the database is started under the AdminServer or DBMAN -start.

Once a startup parameter is configured:

  • The parameter value can be changed in the database Configuration view and is used the next time the database is started.
  • The startup parameter itself cannot be unset (again) from the Configuration view, to be an unused parameter and therefore revert to the default value the database manager uses for unspecified startup parameters. The value entered is taken literally.
For example: If a value for the Before image threshold (-bithold) parameter is inadvertently set, it cannot be unset by changing the value to: 
  • (zero) 0, or
  • the default value displayed initially: (three) 3 MB.
For this particular startup parameter, the database will fail to start unable to initialise the before-image cluster chain (4 x biclustersize) or when the configured clustersize is small enough, it will shutdown shortly after starting as soon as more biclusters are added to record the online transaction processing notes.

The bithold value will need to be changed through the configuration settings to some more reasonably sized value (MB) to restrict the before-image file from unlimited growth.

To unset a managed database startup parameter:

a. Edit the <DLC>\properties\conmgr.properties file and remove the entire lines bithold=<n> and beforeimagestall:
 #  beforeimagestall=true
 #  bithold=3

Manual updates directly in the properties file are detected and used the next time the managed database is started. However if the properties file is overwritten (with another copy), changes are not recognised until the AdminServer is re-started.  For further information refer to Article:
a. Restart the AdminServer.
The default display value is back under the database configuration settings:
Before image threshold (-bithold) 3


 
Workaround
Notes
Last Modified Date11/20/2020 6:55 AM
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