Calling SQLSetPos

In ODBC 2.x, the pointer to the row status array was an argument to SQLExtendedFetch. The row status array was later updated by a call to SQLSetPos. Some drivers have relied on the fact that this array does not change between SQLExtendedFetch and SQLSetPos. In ODBC 3.x, the pointer to the status array is a descriptor field and so the application can easily change it to point to a different array. This can be a problem when an ODBC 3.x application is working with an ODBC 2.x driver, but is calling SQLSetStmtAttr to set the array status pointer and is calling SQLFetchScroll to fetch data. The Driver Manager maps it as a sequence of calls to SQLExtendedFetch. In the following code, an error would normally be raised when the Driver Manager maps the second SQLSetStmtAttr call when working with an ODBC 2.x driver:

SQLSetStmtAttr(hstmt, SQL_ATTR_ROW_STATUS_PTR, rgfRowStatus, 0);
SQLFetchScroll(hstmt, fFetchType, iRow);
SQLSetStmtAttr(hstmt, SQL_ATTR_ROW_STATUS_PTR, rgfRowStat1, 0);
SQLSetPos(hstmt, iRow, fOption, fLock);

The error would be raised if there were no way to change the row status pointer in ODBC 2.x between calls to SQLExtendedFetch. Instead, the Driver Manager performs the following steps when working with an ODBC 2.x driver:

1. Initializes an internal Driver Manager flag fSetPosError to TRUE.
   
   
2. When an application calls SQLFetchScroll, the Driver Manager sets fSetPosError to FALSE.
   
   
3. When the application calls SQLSetStmtAttr to set SQL_ATTR_ROW_STATUS_PTR, the Driver Manager sets fSetPosError equal to TRUE.
   
   
4. When the application calls SQLSetPos, with fSetPosError equal to TRUE, the Driver Manager raises SQL_ERROR with SQLSTATE HY011 (Attribute cannot be set now) to indicate that the application attempted to call SQLSetPos after changing the row status pointer, but prior to calling SQLFetchScroll.