Sensitive cursors

Question

Moved this post from the SQL PL/SQL forum. Apologies if you had to read this twice..
All,
I have a rather general question about oracle support for sensitive cursors, I need to establish a scrollable result set and "see" changes to the selected data, updated by a different process. There is some mention of oracle support for scrollable cursors that are sensitive, implemented in the JDBC driver.
Is there something similar that I could use to enhance my OPEN cursor implementation in OCI.
thanks in advance,
badri

Answer 1

A scrollable cursor provides support for forward and backward access into the result set from a given position, using either absolute or relative row number offsets into the result set.
You can use scrollable cursor to see updated data if client side Caching is not used.
Oracle does not support DML operations on scrollable cursors. A cursor cannot be made scrollable if the LONG datatype is part of the select list.
Moreover, fetches from a scrollable statement handle are based on the snapshot at execution time. OCI client prefetching works with OCI scrollable cursors. The size of the client prefetch cache can be controlled by the existing OCI attributes OCI_ATTR_PREFETCH_ROWS and OCI_ATTR_PREFETCH_MEMORY.
Example of Access on a Scrollable Cursor
Assume that a result set is returned by the SQL query:
SELECT empno, ename FROM emp
and that the table EMP has 14 rows. One use of scrollable cursors is:
/* execute the scrollable cursor in the scrollable mode */
OCIStmtExecute(svchp, stmthp, errhp, (ub4)0, (ub4)0, (CONST OCISnapshot *)NULL,
(OCISnapshot *) NULL, OCI_STMT_SCROLLABLE_READONLY );
/* Fetches rows with absolute row numbers 6, 7, 8. After this call,
OCI_ATTR_CURRENT_POSITION = 8, OCI_ATTR_ROW_COUNT = 8 */
checkprint(errhp, OCIStmtFetch2(stmthp, errhp, (ub4) 3,
OCI_FETCH_ABSOLUTE, (sb4) 6, OCI_DEFAULT);
/* Fetches rows with absolute row numbers 6, 7, 8. After this call,
OCI_ATTR_CURRENT_POSITION = 8, OCI_ATTR_ROW_COUNT = 8 */
checkprint(errhp, OCIStmtFetch2(stmthp, errhp, (ub4) 3,
OCI_FETCH_RELATIVE, (sb4) -2, OCI_DEFAULT);
/* Fetches rows with absolute row numbers 14. After this call,
OCI_ATTR_CURRENT_POSITION = 14, OCI_ATTR_ROW_COUNT = 14 */
checkprint(errhp, OCIStmtFetch2(stmthp, errhp, (ub4) 1,
OCI_FETCH_LAST, (sb4) 0, OCI_DEFAULT);
/* Fetches rows with absolute row number 1. After this call,
OCI_ATTR_CURRENT_POSITION = 1, OCI_ATTR_ROW_COUNT = 14 */
checkprint(errhp, OCIStmtFetch2(stmthp, errhp, (ub4) 1,
OCI_FETCH_FIRST, (sb4) 0, OCI_DEFAULT);
/* Fetches rows with absolute row numbers 2, 3, 4. After this call,
OCI_ATTR_CURRENT_POSITION = 4, OCI_ATTR_ROW_COUNT = 14 */
checkprint(errhp, OCIStmtFetch2(stmthp, errhp, (ub4) 3,
OCI_FETCH_NEXT, (sb4) 0, OCI_DEFAULT);
/* Fetches rows with absolute row numbers 3,4,5,6,7. After this call,
OCI_ATTR_CURRENT_POSITION = 7, OCI_ATTR_ROW_COUNT = 14. It is assumed
the user's define memory is allocated. */
checkprint(errhp, OCIStmtFetch2(stmthp, errhp, (ub4) 5,
OCI_FETCH_PRIOR, (sb4) 0, OCI_DEFAULT);
checkprint (errhp, status)
ub4 rows_fetched;
/* This checks for any OCI errors before printing the results of the fetch call
in the define buffers */
checkerr (errhp, status);
checkerr(errhp, OCIAttrGet((CONST void *) stmthp, OCI_HTYPE_STMT,
(void *) &rows_fetched, (uint *) 0, OCI_ATTR_ROWS_FETCHED, errhp));
...