Retentive attribute properties and behavior

Some changes that are made to attributes at run time are automatically tracked and saved. These attributes are called "retentive attributes." Changes made at run time to retentive attributes are automatically retained. If an object with a retentive attribute is undeployed and subsequently redeployed with the Preserve Runtime Changes option selected in the Deploy dialog, the last run time value is loaded into the retentive attribute. If the Preserve Runtime Changes option is NOT selected, the object is redeployed with its configured setting, not the value set during run time. See Deploy objects for additional information.

Changes to retentive attributes are retained as long as the new attribute value is different than the previous saved value, and data quality of the attribute is good. You do not have to do anything to mark an attribute as a retentive attribute. Attributes are automatically set to be retentive if all of the following are true:

• The attribute is checkpointed.

• The attribute is User- or Object-Writeable.

• The attribute does not contain an input extension or input/output extension.

At every checkpoint period, the AppEngine looks for changes to retentive attributes on objects that it hosts. A change made at run time to a retentive attribute is saved on the node where the AppEngine is running. When any of the retentive attributes associated with the AppEngine have been changed, the changed values are loaded into memory. After several checkpoint periods have passed, the changed values in memory are written to disk, and memory is cleared. In this way, only values that have changed are retained. However, retentive attribute run time changes are not uploaded to the IDE. Therefore, if an object that contains a retentive attribute is undeployed and moved to a different node or even to a different AppEngine, the run time changes are not preserved when the object is redeployed.

For redundant pairs, changes will be preserved, even if the redundant partner is on a different engine or node. If the value of a retentive attribute changes and it is part of a redundant pair, the changed value will be sent to the redundant partner during checkpoint synchronization, if the following are both true:

• Attribute data quality is good

• The new attribute value is different than the previous value

See Redundancy for more information.