ORA-24810 on writing blob via Pro*C

Question

I'm using Oracle Pro*C with an Oracle 9.2 RDBMS.
I am trying to store a blob from a file using Pro*C. If the file is small enough that I can read/write the entire file in a single operation, it blow write works okay. However, I would like to be able to handle a blob of any size, up to 4MB. Unless, I use a 4MB io buffer, this requires partial file read / blob writes. In the program before, the initial write (first) works, but subsequent writes (next) fail with the 24810 attempting to write more data than indicated error. I cannot find a worthwhile explanation for this error - what does it mean?
Here is my sample program.
#include <oci.h>
#include <stdio.h>
#define CMN_IO_BUFF_SIZE 4096
EXEC SQL INCLUDE sqlca.h;
EXEC SQL INCLUDE oraca.h;
EXEC SQL BEGIN DECLARE SECTION;
VARCHAR f_Conn[100];
EXEC SQL END DECLARE SECTION;
int main () {
OCIBlobLocator *DbBlob;
FILE          *Fp;
int          FirstRead;
unsigned int     BytesRead;
unsigned int     Offset;
unsigned char     IoBuff[CMN_IO_BUFF_SIZE];
strcpy ( f_Conn.arr, "isis_app/isis_app@isisdev1" );
f_Conn.len = strlen ( f_Conn.arr );
EXEC SQL VAR IoBuff IS RAW ( CMN_IO_BUFF_SIZE );
printf ( "VAR returned error %d\n", sqlca.sqlcode );
printf ( " %s\n", sqlca.sqlerrm.sqlerrmc );
EXEC SQL CONNECT :f_Conn;
printf ( "CONNECT returned error %d\n", sqlca.sqlcode );
printf ( " %s\n", sqlca.sqlerrm.sqlerrmc );
EXEC SQL ALLOCATE :DbBlob;
printf ( "ALLOC returned error %d\n", sqlca.sqlcode );
printf ( " %s\n", sqlca.sqlerrm.sqlerrmc );
EXEC SQL INSERT INTO lob_table (a_blob)
VALUES (EMPTY_BLOB())
RETURNING a_blob INTO :DbBlob;
printf ( "INSERT returned error %d\n", sqlca.sqlcode );
printf ( " %s\n", sqlca.sqlerrm.sqlerrmc );
Fp = fopen ( "test.gif", "r" );
if ( Fp != 0 ) {
FirstRead = 1;
Offset = 1;
BytesRead = CMN_IO_BUFF_SIZE;
while ( BytesRead > 0 ) {
printf ( "Bytes requested %d\n", BytesRead );
BytesRead = fread ( IoBuff, 1, BytesRead, Fp );
printf ( "Bytes read %d\n", BytesRead );
if ( ( FirstRead == 1 ) && ( BytesRead < CMN_IO_BUFF_SIZE ) ) {
EXEC SQL LOB WRITE ONE :BytesRead
FROM :IoBuff INTO :DbBlob AT :Offset;
printf ( "WRITE ONE returned error %d\n", sqlca.sqlcode );
printf ( " %s\n", sqlca.sqlerrm.sqlerrmc );
printf ( "Bytes written %d at offset %d\n", BytesRead, Offset );
} else if ( ( FirstRead == 1 ) && ( BytesRead == CMN_IO_BUFF_SIZE ) ) {
EXEC SQL LOB WRITE FIRST :BytesRead
FROM :IoBuff INTO :DbBlob AT :Offset;
printf ( "WRITE FIRST returned error %d\n", sqlca.sqlcode );
printf ( " %s\n", sqlca.sqlerrm.sqlerrmc );
printf ( "Bytes written %d at offset %d\n", BytesRead, Offset );
} else if ( ( FirstRead == 0 ) && ( BytesRead == CMN_IO_BUFF_SIZE ) ) {
EXEC SQL LOB WRITE NEXT :BytesRead
FROM :IoBuff INTO :DbBlob AT :Offset;
printf ( "WRITE NEXT returned error %d\n", sqlca.sqlcode );
printf ( " %s\n", sqlca.sqlerrm.sqlerrmc );
printf ( "Bytes written %d at offset %d\n", BytesRead, Offset );
} else if ( ( FirstRead == 0 ) && ( BytesRead < CMN_IO_BUFF_SIZE ) ) {
EXEC SQL LOB WRITE LAST :BytesRead
FROM :IoBuff INTO :DbBlob AT :Offset;
printf ( "WRITE LAST returned error %d\n", sqlca.sqlcode );
printf ( " %s\n", sqlca.sqlerrm.sqlerrmc );
printf ( "Bytes written %d at offset %d\n", BytesRead, Offset );
FirstRead = 0;
Offset = Offset + BytesRead;
if ( BytesRead < CMN_IO_BUFF_SIZE ) {
BytesRead = 0;
fclose ( Fp );
} else {
printf ( "Error opening input file\n" );
EXEC SQL COMMIT WORK;
printf ( "COMMIT returned error %d\n", sqlca.sqlcode );
printf ( " %s\n", sqlca.sqlerrm.sqlerrmc );
}

Answer 1

Do not use buffered IO (FILE*) . Use direct Calls(Open/Write).
Buffered IO has limiations