Abort of a OCILobRead() (streaming mode)

Question

I have a problem on canceling a sequence of OCILobRead() calls. They are in streaming mode, setting the amtp parameter to 0, and calling it over and over again as long as OCILobRead() returns OCI_NEED_DATA.
According to the documentation, a sequence of those calls can be aborted with OCIBreak(), but this does not work in my case. The OCIBreak call returns without error, but the next OCI operation on that connection fails with:
ORA-03127 no new operations allowed until the active operation ends.
I tried it in both blocking mode and nonblocking mode, but the resulting error is the same.
Any help would be appreciated.

Answer 1

I tried that, but it doesn't work too. I dont get the mentioned error ORA-01013, but the additional OCILobRead returns again OCI_NEED_DATA.
It seems that the OCIBreak had no influence at all on the sequence of calls.
I extracted the code to a small test program, maybe i missed something during initialization (mode???), or statement prep?
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <oci.h>
static OCIEnv*     oci_env     = NULL;  // Environment handle
static OCISvcCtx*  oci_svcctx  = NULL;  // Service handle
static OCIServer*  oci_server  = NULL;  // Server handles
static OCIError*   oci_error   = NULL;  // Error handle
static OCISession* oci_session = NULL;  // Session handle
static OCIStmt*    oci_stmt    = NULL;  // Statement handle
void checkerr(sword status)
  switch (status)
    case OCI_SUCCESS:
      break;
    case OCI_SUCCESS_WITH_INFO:
      printf("Info - OCI_SUCCESS_WITH_INFO\n");
      break;
    case OCI_NEED_DATA:
      printf("Info - OCI_NEED_DATA\n");
      break;
    case OCI_NO_DATA:
      printf("Info - OCI_NODATA\n");
      break;
    case OCI_ERROR:
      text  errbuf[1024];
      sb4   errcode = 0;
      OCIErrorGet(oci_error, 1, NULL, &errcode, errbuf, sizeof(errbuf), OCI_HTYPE_ERROR);
      printf("Error - %s\n", errbuf);
      break;
    case OCI_INVALID_HANDLE:
      printf("Error - OCI_INVALID_HANDLE\n");
      break;
    case OCI_STILL_EXECUTING:
      printf("Info - OCI_STILL_EXECUTE\n");
      break;
    case OCI_CONTINUE:
      printf("Error - OCI_CONTINUE\n");
      break;
    default:
      break;
void logon(char* user, char* pass, char* host)
  // allocate environment handle
  checkerr(OCIEnvCreate(&oci_env, OCI_DEFAULT, NULL, NULL, NULL, NULL, 0, NULL));
  // allocate error handle
  checkerr(OCIHandleAlloc(oci_env, (dvoid**)&oci_error, OCI_HTYPE_ERROR, 0, NULL));
  // allocate server handle
  checkerr(OCIHandleAlloc(oci_env, (dvoid**)&oci_server, OCI_HTYPE_SERVER, 0, NULL));
  // allocate service context
  checkerr(OCIHandleAlloc(oci_env, (dvoid**)&oci_svcctx, OCI_HTYPE_SVCCTX, 0, NULL));
  checkerr(OCIServerAttach(oci_server, oci_error, (text*)host, strlen(host), 0));
  // set attribute server context in the service context
  checkerr(OCIAttrSet(oci_svcctx, OCI_HTYPE_SVCCTX, oci_server, 0, OCI_ATTR_SERVER, oci_error));
  // allocate session handle
  checkerr(OCIHandleAlloc(oci_env, (dvoid**)&oci_session, OCI_HTYPE_SESSION, 0, NULL));
  // set attributes username and password in the session context
  checkerr(OCIAttrSet(oci_session, OCI_HTYPE_SESSION, user, strlen(user), OCI_ATTR_USERNAME, oci_error));
  checkerr(OCIAttrSet(oci_session, OCI_HTYPE_SESSION, pass, strlen(pass), OCI_ATTR_PASSWORD, oci_error));
  // begin session
  checkerr(OCISessionBegin(oci_svcctx, oci_error, oci_session, OCI_CRED_RDBMS, OCI_DEFAULT));
  checkerr(OCIAttrSet(oci_svcctx, OCI_HTYPE_SVCCTX, oci_session, 0, OCI_ATTR_SESSION, oci_error));
void logoff()
  checkerr(OCISessionEnd(oci_svcctx, oci_error, oci_session, OCI_DEFAULT));
  checkerr(OCIServerDetach(oci_server, oci_error, OCI_DEFAULT));
  /* free handles */
  if (oci_session)
    OCIHandleFree(oci_session, OCI_HTYPE_SESSION);
  if (oci_svcctx)
    OCIHandleFree(oci_svcctx, OCI_HTYPE_SVCCTX);
  if (oci_server)
    OCIHandleFree(oci_server, OCI_HTYPE_SERVER);
  if (oci_error)
    OCIHandleFree(oci_error, OCI_HTYPE_ERROR);
  if (oci_stmt)
    OCIHandleFree(oci_stmt, OCI_HTYPE_STMT);
  if (oci_env)
    OCIHandleFree(oci_env, OCI_HTYPE_ENV);
int checkout()
  text*          select = (text*) "SELECT blob_obj FROM te_rblock WHERE te_rblock.obj_id = '301000xxx:1:1'";
  OCIDefine*     oci_define;
  OCILobLocator* oci_lob;
  ub2            oci_ind, oci_rlen, oci_rcode;
  checkerr(OCIHandleAlloc(oci_env, (dvoid**)&oci_stmt, OCI_HTYPE_STMT, 0, NULL));
  checkerr(OCIStmtPrepare(oci_stmt, oci_error, select, strlen((char*)select), (ub4)OCI_NTV_SYNTAX, (ub4)OCI_DEFAULT));
  checkerr(OCIDescriptorAlloc(oci_env, (void**)&oci_lob, OCI_DTYPE_LOB, 0, NULL));
  checkerr(OCIDefineByPos(oci_stmt, &oci_define, oci_error, 1, &oci_lob, 0, SQLT_BLOB, &oci_ind, &oci_rlen, &oci_rcode, OCI_DEFAULT));
  checkerr(OCIStmtExecute(oci_svcctx, oci_stmt, oci_error, 1, 0, NULL, NULL, OCI_DEFAULT));
  ub4       offset = 1;
  ub4       amount = 0;
  const ub4 PIECE_SIZE = 128;
  ub4       piece_len = PIECE_SIZE;
  char      piece[PIECE_SIZE + 1];
  int       counter = 0;
  sword     ret = OCI_NEED_DATA;
  while (ret == OCI_NEED_DATA)
    checkerr(ret = OCILobRead(oci_svcctx, oci_error, oci_lob, &amount, offset, piece, piece_len, NULL, NULL, 0, SQLCS_IMPLICIT));
    // if we dont interrupt it, everything is ok
    if (++counter == 5)
      checkerr(OCIBreak(oci_svcctx, oci_error));
      break;
  checkerr(OCIHandleFree(oci_stmt, OCI_HTYPE_STMT));
  oci_stmt = NULL;
  return 0;
int main(int argc,char* argv[])
  if (argc != 4)
    printf("usage: %s <dbuser> <pwd> <db>\n", argv[0]);
    return -1;
  logon(argv[1], argv[2], argv[3]);
  // first checkout works fine
  checkout();
  // second time ORA-03127 occurs!!
  checkout();
  logoff();
  return 0;