diff --git a/src/client/inc/tsclient.h b/src/client/inc/tsclient.h
index bdb35cb07274a880c98aa2c93005c47fe05c7de2..f2a9b9db43a854ed11e421daedcf66f907622f19 100644
--- a/src/client/inc/tsclient.h
+++ b/src/client/inc/tsclient.h
@@ -285,8 +285,8 @@ typedef struct {
   char **        buffer;  // Buffer used to put multibytes encoded using unicode (wchar_t)
   SColumnIndex*  pColumnIndex;
 
-  SArithmeticSupport*   pArithSup;   // support the arithmetic expression calculation on agg functions
-  struct SLocalReducer* pLocalReducer;
+  SArithmeticSupport   *pArithSup;   // support the arithmetic expression calculation on agg functions
+  struct SLocalReducer *pLocalReducer;
 } SSqlRes;
 
 typedef struct STscObj {
diff --git a/src/client/src/tscLocal.c b/src/client/src/tscLocal.c
index 4c28adc261f6b83b3c1bbb68d3dd3d56e6007fc9..ab52ef396b57e63a20060e2346d2052e9b851c64 100644
--- a/src/client/src/tscLocal.c
+++ b/src/client/src/tscLocal.c
@@ -46,7 +46,8 @@ typedef struct SCreateBuilder {
   SSqlObj *pInterSql;
   int32_t (*fp)(void *para, char* result);
   Stage callStage;
-} SCreateBuilder; 
+} SCreateBuilder;
+
 static void tscSetLocalQueryResult(SSqlObj *pSql, const char *val, const char *columnName, int16_t type, size_t valueLength);
 
 static int32_t tscSetValueToResObj(SSqlObj *pSql, int32_t rowLen) {
@@ -207,10 +208,7 @@ static int32_t tscProcessDescribeTable(SSqlObj *pSql) {
   const int32_t TYPE_COLUMN_LENGTH = 16;
   const int32_t NOTE_COLUMN_MIN_LENGTH = 8;
 
-  int32_t noteFieldLen = NOTE_COLUMN_MIN_LENGTH;//tscMaxLengthOfTagsFields(pSql);
-//  if (noteFieldLen == 0) {
-//    noteFieldLen = NOTE_COLUMN_MIN_LENGTH;
-//  }
+  int32_t noteFieldLen = NOTE_COLUMN_MIN_LENGTH;
 
   int32_t rowLen = tscBuildTableSchemaResultFields(pSql, NUM_OF_DESC_TABLE_COLUMNS, TYPE_COLUMN_LENGTH, noteFieldLen);
   tscFieldInfoUpdateOffset(pQueryInfo);
@@ -822,26 +820,36 @@ static int32_t tscProcessClientVer(SSqlObj *pSql) {
 
 }
 
+// TODO add test cases.
+static int32_t checkForOnlineNode(SSqlObj* pSql) {
+  int32_t* data = pSql->res.length;
+
+  int32_t total  = data[0];
+  int32_t online = data[1];
+  return (online < total)? TSDB_CODE_RPC_NETWORK_UNAVAIL:TSDB_CODE_SUCCESS;
+}
+
 static int32_t tscProcessServStatus(SSqlObj *pSql) {
   STscObj* pObj = pSql->pTscObj;
 
   SSqlObj* pHb = (SSqlObj*)taosAcquireRef(tscObjRef, pObj->hbrid);
   if (pHb != NULL) {
-    int32_t code = pHb->res.code;
+    pSql->res.code = pHb->res.code;
     taosReleaseRef(tscObjRef, pObj->hbrid);
-    if (code == TSDB_CODE_RPC_NETWORK_UNAVAIL) {
-      pSql->res.code = TSDB_CODE_RPC_NETWORK_UNAVAIL;
-      return pSql->res.code;
-    }
-  } else {
-    if (pSql->res.code == TSDB_CODE_RPC_NETWORK_UNAVAIL) {
-      return pSql->res.code;
-    }
   }
 
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
+  if (pSql->res.code == TSDB_CODE_RPC_NETWORK_UNAVAIL) {
+    return pSql->res.code;
+  }
+
+  pSql->res.code = checkForOnlineNode(pHb);
+  if (pSql->res.code == TSDB_CODE_RPC_NETWORK_UNAVAIL) {
+    return pSql->res.code;
+  }
 
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
   SSqlExpr* pExpr = taosArrayGetP(pQueryInfo->exprList, 0);
+
   int32_t val = 1;
   tscSetLocalQueryResult(pSql, (char*) &val, pExpr->aliasName, TSDB_DATA_TYPE_INT, sizeof(int32_t));
   return TSDB_CODE_SUCCESS;
diff --git a/src/client/src/tscServer.c b/src/client/src/tscServer.c
index 994dace1e3f5c129970efefbceee806d0e803c82..f450f4aa4052f69e7c6dfb535c9afa15ded5b176 100644
--- a/src/client/src/tscServer.c
+++ b/src/client/src/tscServer.c
@@ -147,15 +147,15 @@ void tscProcessHeartBeatRsp(void *param, TAOS_RES *tres, int code) {
   SSqlObj *pSql = tres;
   SSqlRes *pRes = &pSql->res;
 
-  if (code == 0) {
+  if (code == TSDB_CODE_SUCCESS) {
     SHeartBeatRsp *pRsp = (SHeartBeatRsp *)pRes->pRsp;
-    SRpcEpSet *    epSet = &pRsp->epSet;
+    SRpcEpSet     *epSet = &pRsp->epSet;
     if (epSet->numOfEps > 0) {
       tscEpSetHtons(epSet);
       if (!tscEpSetIsEqual(&pSql->pTscObj->tscCorMgmtEpSet->epSet, epSet)) {
         tscTrace("%p updating epset: numOfEps: %d, inUse: %d", pSql, epSet->numOfEps, epSet->inUse);
         for (int8_t i = 0; i < epSet->numOfEps; i++) {
-          tscTrace("endpoint %d: fqdn = %s, port=%d", i, epSet->fqdn[i], epSet->port[i]);
+          tscTrace("endpoint %d: fqdn=%s, port=%d", i, epSet->fqdn[i], epSet->port[i]);
         }
         tscUpdateMgmtEpSet(pSql, epSet);
       }
@@ -167,11 +167,40 @@ void tscProcessHeartBeatRsp(void *param, TAOS_RES *tres, int code) {
       tscKillConnection(pObj);
       return;
     } else {
-      if (pRsp->queryId) tscKillQuery(pObj, htonl(pRsp->queryId));
-      if (pRsp->streamId) tscKillStream(pObj, htonl(pRsp->streamId));
+      if (pRsp->queryId) {
+        tscKillQuery(pObj, htonl(pRsp->queryId));
+      }
+
+      if (pRsp->streamId) {
+        tscKillStream(pObj, htonl(pRsp->streamId));
+      }
+    }
+
+    int32_t total  = htonl(pRsp->totalDnodes);
+    int32_t online = htonl(pRsp->onlineDnodes);
+    assert(online <= total);
+
+    if (online < total) {
+      tscError("HB:%p, total dnode:%d, online dnode:%d", pSql, total, online);
+      pSql->res.code = TSDB_CODE_RPC_NETWORK_UNAVAIL;
     }
+
+    if (pRes->buffer == NULL) {
+      pRes->length = calloc(2,  sizeof(int32_t));
+    }
+
+    pRes->length[0] = total;
+    pRes->length[1] = online;
   } else {
     tscDebug("%" PRId64 " heartbeat failed, code:%s", pObj->hbrid, tstrerror(code));
+    if (pRes->buffer == NULL) {
+      pRes->length = calloc(2, sizeof(int32_t));
+    }
+
+    pRes->length[1] = 0;
+    if (pRes->length[0] == 0) {
+      pRes->length[0] = 1; // make sure that the value of the total node is greater than the online node
+    }
   }
 
   if (pObj->hbrid != 0) {