Compiler warning PLW-05003 parameter at IN and COPY may have side effects

Question

For the following Procedure:
create or replace
PROCEDURE lob_replace
p_lob IN OUT NOCOPY CLOB,
p_what IN VARCHAR2,
p_with IN VARCHAR2 )
AS
n NUMBER;
BEGIN
dbms_output.put_line('p_what = ' || p_what);
dbms_output.put_line('p_with = ' || p_with);
n := dbms_lob.instr( p_lob, p_what );
dbms_output.put_line('n = ' || n);
IF ( NVL(n,0) > 0 ) THEN
dbms_lob.copy( p_lob, p_lob, dbms_lob.getlength(p_lob), n+LENGTH(p_with), n+LENGTH(p_what) );
dbms_lob.write( p_lob, LENGTH(p_with), n, p_with );
IF ( LENGTH(p_what) > LENGTH(p_with) ) THEN
dbms_lob.trim( p_lob, dbms_lob.getlength(p_lob)-(LENGTH(p_what)-LENGTH(p_with)) );
END IF;
END IF;
END;
When I compile this, I receive the following warning "Warning(15,5): PLW-05003: same actual parameter(P_LOB and P_LOB) at IN and NOCOPY may have side effect"
Line 15, column 5 is:
dbms_lob.copy( p_lob, p_lob, dbms_lob.getlength(p_lob), n+LENGTH(p_with), n+LENGTH(p_what) );
I'm reading about the NOCOPY Compiler hint at
http://download-west.oracle.com/docs/cd/B10501_01/appdev.920/a96624/08_subs.htm#12813 but I'm not for sure what exactly the issue is here?
The syntax for dbms_lob.copy is:
DBMS_LOB.COPY (
dest_lob IN OUT NOCOPY BLOB,
src_lob IN BLOB,
amount IN INTEGER,
dest_offset IN INTEGER := 1,
src_offset IN INTEGER := 1);
Do I need to copy the p_lob to another variable, not sure what do here?

Answer 1

Hi,
Is this really a stand alone procedure, or is it in fact part of a package?
That warning usually comes when parameter is declared with NOCOPY in specification but without in body. Or vice versa.
Could this be the case?
Regards
Peter