ORA-06571: Function CALC_AVG does not guarantee not to update database

I have written this as a function and as a package. The function works just fine, but when I try to call the same function within a package I get this error. Any Suggestons? There is nothing but select statemnts in the function just calculating an average against criteria that I can use in a view.

Function CALC_AVG (CTID in varchar2, ASSAYTR in varchar2, ATYPE in varchar2)

return number

is

TRP_AVG NUMBER(8,3); BEGIN  select avg(decode(operator,'=',result,null))

into

 TRP_AVG from

 secondary_results

where

 assayid = ASSAYTR and
 sampleid = CTID and
 datatype = ATYPE;

return (TRP_AVG); Received on Mon Oct 11 1999 - 12:04:30 CDT