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  • Type
    • The type of History Store with options of In-Memory and Disk-Backed
    • Data stored in an In-Memory History Store will not be persisted across a module disable/enable, module restart or power loss. 
    • Data stored in a Disk-Backed History Store will persist across a module disable/enable, module restart or power loss.
  • Edge Node Tag Capacity
    • Maximum number of Edge Node level tag change events to store per Edge Node before dropping oldest historical Edge Node tag change events. This value is independent of the 'Device Tag Capacity' and only applies to how many 'Edge Node level' tag change events are stored per Edge Node.
    • Default 100,000
    • A tag change event is triggered by either a change in value or quality and results in the tag's Qualified Value (which has three attributes of value, quality and timestamp) being stored. 
  • Device Tag Capacity
    • Maximum number of Device tag change events to store per Device before dropping oldest historical Device tag change events. This value is independent of the 'Edge Node Tag Capacity' and only applies to how many 'Device level' tag change events are stored per Device.
    • Default 10,000
    • A tag change event is triggered by either a change in value or quality and results in the tag's Qualified Value (which has three attributes of value, quality and timestamp) being stored.
  • Flush Quantity
    • The maximum number of tags to publish in a single message upon reestablishing communication.
    • Default 10,000
  • Flush Period
    • The period to wait in milliseconds between publishes when flushing messages upon reestablishing communication.
    • Default 200



Info

Large Tag Capacities

If using a large tag capacity it is highly recommended to test the system under load in a non-production environment on similar hardware and software that will be used in production. During testing is also important to get the system into a state where the store and forward cache becomes full before beginning to flush. This will ensure that the system is sized appropriately when deployed into a production environment. There are a number of factors involved in determining how large the tag capacity can be including but not limited to system resources such as CPU, RAM (especially when using 'In-Memory'), Disk IOPS (if using 'Disk-Backed'), the nominal tag change rate (e.g. number of tags changing per second in the system), the flush rate, bandwidth availability, whether flushing in order vs asynchronously, etc. Because of the complex interactions of these variables it is highly recommended to test in a controlled environment. Generally any capacity over 2,000,000 is considered large and should be tested before deploying to production.


How to determine these settings

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