Concept Property History
Each concept property includes a history, the size of which is configurable.
The history size determines how many previous values TIBCO BusinessEvents stores for that property. You can also set the history policy to record all values or only changed values.
- ConceptReference Properties History is tracked when a contained or referenced concept instance changes to a different concept instance. History is not tracked, however, when a contained or referenced concept’s properties change. See Inheritance Relationships for more on containment and reference relationships.
- Database concept properties do not support history tracking.
If you set the history size to one or more, TIBCO BusinessEvents stores the property value when the property changes, along with a date and timestamp, up to the number specified. When the maximum history size is reached, the oldest values are discarded as new values are recorded.
If you set the history size to 0, TIBCO BusinessEvents does not store historical values for the concept. It stores the value without a time and date stamp.
For example, consider a Customer concept:
Property Name | History | Comments |
---|---|---|
customer_name | 1 | These properties tend to be very stable and you may have little interest in tracking a history for them. |
customer_address | 1 | |
city | 1 | |
state | 1 | |
zip | 1 | |
account_number | 0 | With history size 0, TIBCO BusinessEvents does not record the timestamp when the value is set. |
credit_limit | 4 | Credit limit may change more frequently and you may have an interest in tracking the changes. |
Historical Values are Stored in a Ring Buffer
The historical values for a concept property are kept in a ring buffer. The ring buffer stores both the value and the time at which the value was recorded. After the ring buffer reaches maximum capacity, which is eight in this example, TIBCO BusinessEvents begins replacing older values such that it always stores the n most recent values, where n is the history size.
TIBCO BusinessEvents can record values using either of these policies:
- Changes Only - TIBCO BusinessEvents records the value of the property every time it changes to a new value.
- All Values - TIBCO BusinessEvents records the value of the property every time an action sets the value even if the new value is the same as the old value.
Which you choose depends on what you are tracking. For example, if you are setting the history for a property that tracks how many people pass a sensor every five minutes, All Values might be the best policy. However, if you are setting the history for a property that tracks the level of liquid in a coffee pot, Changes Only might be more appropriate.