The Workflow Engine threshold is set to 50 as a default. Activities with a cost higher than 50 are deferred for background engines to process.
In some cases, you may want to force the engine to defer an activity although the activity's cost is less than fifty. You can do this by altering the Workflow Engine threshold in the PL/SQL stored procedure for a function activity.
The engine threshold is set in an externalized constant called THRESHOLD. Include the following line in your PL/SQL procedure to set the WF Engine threshold to a different value:
WF_ENGINE.THRESHOLD := n;
You should reset the threshold value afterwards in SQLPLUS or in the next function activity so that other activities are processed as expected.
See: Setting Up Background Engines