I've just finished debugging a strange problem in a page process that was giving incorrect results because a page item had the wrong value. We discovered this page item value was getting set as soon as the user's session was created and even before he loaded that page. The V() function would return a value for this item even when there was no value in WWV_FLOW_DATA.
Eventually, I turned on session tracing and found this when V('P1_ITEM') was being called:
SELECT ATTRIBUTE_VALUE FROM WWV_FLOW_PREFERENCES$ WHERE USER_ID=:B3 AND SECURITY_GROUP_ID = :B2 AND PREFERENCE_NAME = 'PERSISTENT_ITEM_'||:B1
There was indeed a value in WWV_FLOW_PREFERENCES$ for PERSISTENT_ITEM_P1_ITEM. We don't really use preferences except for the usual built in report sorting and this "persistent_item" type of preference is new to me. Even when I deliberately set a preference (apex_util.set_preference), it does not add this prefix.
I can't find anything in the documentation on this. Does anyone know what this might be?
This is on Apex 5.1.2.