You can use Standard or Block Transaction Groups to create recipe management system with bi-directional communication to pass database information to the PLC when requested. The main advantage of using transaction groups to design the recipe management group is that the group will write to all the OPC locations.
To use transaction groups to create recipes
Create a new Standard transaction group.
Drag a set of tags into the group's Basic OPC/Group Items. One of these tags should be a recipe index tag and needs to be read-only.
Change the recipe index tag to read-only by selecting Read-only from the drop-down in the Taget Name column.
Go to the Action tab, and set the following:
Update mode: choose DB to OPC.
Table name: select the table name that contains the recipes. This table should have an index.
Use custom index column: select the check box and choose the column that is the index from the table.
Store timestamp to a column: deselect the check box.
In the Table action area of the Action tab, click update/select and custom to create a custom clause that references the read-only tag. The read-only tag and the name of the index column of the database must be the same. Do not include the word "where" because it is assumed to be part of the enclosed statement.
Click Enable to enable the group and do a File > Save to save the project and start the transaction group.
Test the recipe group by entering a new value into the recipe number (for example, the tag that is mapped to the index of the recipe database). The recipe values will download to the appropriate tags.