Trigger Problem updating same table

I have a trigger which I want to update certain colums of the row being updated based on data entered into the first column. The table is being updated from an external datasource using HS.

Here is my trigger:

CREATE OR REPLACE TRIGGER "SYSADM"."TESTUPDATE" BEFORE
UPDATE ON "Test"
FOR EACH ROW BEGIN
UPDATE "SYSADM"."Test"
SET "SYSADM"."Test"."Name" =
(select "NAME" from JonLP#txt@JonLP
where "ROWNUMBER" = :NEW."RowNumber")
where "SYSADM"."Test"."F_DocumentID" = :NEW."F_DocumentID";
END;

When I attempt to update a column in "Test" I get the following error:

ORA-02041: client database did not begin a transaction
ORA-06512: at "SYSADM.TESTUPDATE", line 2
ORA-04088: error during exacution of trigger "SYSADM.TESTUPDATE"


Any help would be greatly appreciated.