Transaction Group Applications
There are four types of Transaction Groups, and they each handle data a little differently.
- Historical Group - A basic, one-way group that collects a data point from each item, and logs it to a column in the database.
- Standard Group - A flexible, two-way group that can log data to the database, or pull data from the database to write to OPC items or tags.
- Block Group - A standard group with an additional feature: each execution of the group can create, modify, or extract multiple rows from the database table, rather than just one.
- Stored Procedure Group - A group capable of invoking a stored procedure in the database, returning the results of any OUT or INOUT parameters to tags or OPC items.
Learn more about each type of group on the Types of Groups page.
Historical Data Logging
Transaction groups can function as a flexible alternative to the Tag Historian, which is more focused on speed and efficiency than simplicity. The Historical Group is explicitly designed for this purpose, but the Block Group can allow multiple rows to be logged at once.
Recipe Management and Synchronization
Transaction groups can furnish devices connected to Ignition with information stored in a database, based on a parameter from the device or elsewhere. Typically a Standard Group would be used for this application, but Block and Stored Procedure groups can accomplish this as well. See the Recipe example for more details.
More generally, Standard and Block groups can be used to synchronize device or tag data with a database table on a timer or schedule, allowing the database to act as a go-between for another system and a target device, or for the database to reflect realtime values for specified data points.
Block Data Transfers
The Block Group supports the transfer of entire arrays of data to and from the database.
The Stored Procedure Group allows you to use group items as inputs and outputs for your existing Stored Procedures, allowing query specifics to be managed external to Ignition.