Oracle Message PGA-20911 - update transaction is already active with TP string at LU string

ERROR	update transaction is already active with TP string at LU string
CAUSE	Transaction has already been started at LU by a PGAINIT call with synclevel set to 1 or 2. Only one transaction at synclevel 1 or 2 is allowed at any given time.
ACTION	The new transaction is not started. Change your application to start the second update transaction after the first one has completed, or to use a different gateway database link for the second update transaction.