Weak and Strongly Typed Reference Cursors in Reports

Question

Our custom reports has been using a reference cursor. I have inherited the code and not sure why there is a need to use a reference cursor when it can be done by a simple select statements. I see no dynamic select statements passed or any special parameters to reason out for use of reference cursor in our custom reports. Prior developers had reason out the benefits of using reference cursor for performance. I tested this by running a report with reference cursor versus plain select statement and still the report that is using the plain select statement performed better (faster) than the report that has the reference cursor, there is a big difference.
I have seen some disadvantage of using reference cursor on the reports that when there is a database object change even if the package that sourced the reference cursor has not been updated or modified the reports needs to be recompiled each time we get this error message coming from the report server queue:
  Terminated with error: <br>REP-8: Run time error in the PL/SQL development
  environment (DE). PDE-PSD001 Could not resolve reference to <Unknown Program Unit>
  while loading <Unknown> <Unknown>. REP-0008: Unexpected memory error while
  initializing preferences.In 9iAS reports prior version the error is occurring rarely. When we moved to 10.1.2.2.0 reports it appears the error occurs most often. We have made an effort to research about the issue and appears to be a bug. One suggestion is to use a strongly typed reference cursor. I have tried to researched about the difference between a weak and strongly typed reference cursor but failed to understand them. I appreciate any help about examples differentiating a weak versus a strongly typed reference cursors.
Thanks,
Warren

Answer 1

I guess my point, for what it's worth, is that whether you use only a strongly typed REF CURSOR, or whether you also use a weakly typed REF CURSOR, you may still end up getting the REP-0008 error (at least if your report is in .REP format). You can avoid this by using a pipelined function instead (or by putting the SQL directly in the report, or possibly by using .RDF or .JSP format).
To test this, you might:
1. Create a database package with an SQL*Plus script that that looks something like this:
CREATE OR REPLACE PACKAGE TEST AS
    TYPE RECORD_TYPE IS RECORD
        USERNAME ALL_USERS.USERNAME%TYPE
    TYPE TABLE_TYPE IS TABLE OF RECORD_TYPE;
    TYPE WEAKLY_TYPED_REF_CURSOR_TYPE IS REF CURSOR;
    TYPE STRONGLY_TYPED_REF_CURSOR_TYPE IS REF CURSOR RETURN RECORD_TYPE;
    FUNCTION GET_WEAKLY_TYPED_REF_CURSOR RETURN WEAKLY_TYPED_REF_CURSOR_TYPE;
    FUNCTION GET_STRONGLY_TYPED_REF_CURSOR RETURN STRONGLY_TYPED_REF_CURSOR_TYPE;
    FUNCTION GET_PIPELINED_TABLE RETURN TABLE_TYPE PIPELINED;
END TEST;
CREATE OR REPLACE PACKAGE BODY TEST AS
    FUNCTION GET_WEAKLY_TYPED_REF_CURSOR RETURN WEAKLY_TYPED_REF_CURSOR_TYPE
    IS
        cWeaklyTypedRefCursor WEAKLY_TYPED_REF_CURSOR_TYPE;
    BEGIN
        OPEN cWeaklyTypedRefCursor FOR
        SELECT USERNAME FROM ALL_USERS;
        RETURN cWeaklyTypedRefCursor;
    END GET_WEAKLY_TYPED_REF_CURSOR;
    FUNCTION GET_STRONGLY_TYPED_REF_CURSOR RETURN STRONGLY_TYPED_REF_CURSOR_TYPE
    IS
        cStronglyyTypedRefCursor WEAKLY_TYPED_REF_CURSOR_TYPE;
    BEGIN
        OPEN cStronglyyTypedRefCursor FOR
        SELECT USERNAME FROM ALL_USERS;
        RETURN cStronglyyTypedRefCursor;
    END GET_STRONGLY_TYPED_REF_CURSOR;
    FUNCTION GET_PIPELINED_TABLE
    RETURN TABLE_TYPE PIPELINED
    IS
    BEGIN
        FOR rec IN
            SELECT USERNAME FROM ALL_USERS
        LOOP
            PIPE ROW(rec);
        END LOOP;
    END GET_PIPELINED_TABLE;
END TEST;
/2. Create a report based on REF CURSOR query using only a strongly typed REF CURSOR. The PL/SQL statement that you use in the report as the data source for the query might look something like this:
function QR_1RefCurDS return test.strongly_typed_ref_cursor_type is
begin
  return test.get_strongly_typed_ref_cursor;
end;3. Compile the report to a .REP file and run it to make sure it works as expected.
4. Drop and re-create the TEST package in the database.
5. Try running the .REP file again. I expect you will get the REP-0008 error.
6. Modify the REF CURSOR query to use an underlying weakly typed REF CURSOR by changing the PL/SQL statement (from Step 2) to something like this:
function QR_1RefCurDS return test.strongly_typed_ref_cursor_type is
begin
  return test.get_weakly_typed_ref_cursor;
end;7. Repeat Steps 3 through 5. I expect you will get the REP-0008 error again.
8. Replace the REF CURSOR query in report with an SQL query that looks something like this:
SELECT * FROM TABLE(TEST.GET_PIPELINED_TABLE)9. Repeat Steps 3 through 5. I expect you will not get the REP-0008 error.
Hope this helps.