diff --git a/lib/redis.js b/lib/redis.js
index 0234875..b4dc5c6 100644
--- a/lib/redis.js
+++ b/lib/redis.js
@@ -152,9 +152,9 @@ async function call(query, body) {
   const results = [];
   for (let i = 0; i < lines.length; i++) {
     try {
-      results.push(await redis.call(...lines[i]));
+      results.push({error: false, result: await redis.call(...lines[i])});
     } catch (e) {
-      results.push(`${e.message}`);
+      results.push({error: true, message: `${e.message}`});
     }
   }
   return results;
diff --git a/src/app/app.component.ts b/src/app/app.component.ts
index 43242f4..5dac248 100644
--- a/src/app/app.component.ts
+++ b/src/app/app.component.ts
@@ -219,16 +219,20 @@ export class AppComponent implements OnInit {
    */
   onNewValue(newValue) {
     this.redisService.call(newValue.id, [newValue.rawLine]).subscribe(ret => {
-      if (newValue.from === 'root') {
-        this.onRefresh();
-      }
-      if (newValue.onSuccess) {
-        newValue.onSuccess(newValue);
+      if (!ret[0].error) {
+        if (newValue.from === 'root') {
+          this.onRefresh();
+        }
+        if (newValue.onSuccess) {
+          newValue.onSuccess(newValue);
+        }
+        this.util.showMessage(newValue.edit ? 'Updated successfully.' : 'Added successfully.');
+      } else {
+        this.util.showMessage('Failed to add the value: ' + ret[0].message);
       }
-      this.util.showMessage(newValue.edit ? 'Updated successfully.' : 'Added successfully.');
     }, e => {
-      console.error(e.error.message);
-      this.util.showMessage('Fail to add the value: ' + this.util.getErrorMessage(e));
+      this.util.showMessage('Failed to add the value: ' + this.util.getErrorMessage(e));
+      this._store.dispatch(new RedisConnectFailed({id: this.pageData.id}))
     });
   }
 
diff --git a/src/app/components/add-value-dialog/add-value-dialog.component.ts b/src/app/components/add-value-dialog/add-value-dialog.component.ts
index c3e0ccb..dfadd8c 100644
--- a/src/app/components/add-value-dialog/add-value-dialog.component.ts
+++ b/src/app/components/add-value-dialog/add-value-dialog.component.ts
@@ -173,18 +173,6 @@ export class AddValueDialogComponent implements OnInit {
     }
   }
 
-  /**
-   * remove exist key
-   * @param ret the ret include id and key
-   * @param cb the callback
-   */
-  removeExistKey(ret, cb) {
-    this.redisService.call(ret.id, [['DEL', ret.key]]).subscribe(() => {
-      cb();
-    }, err => {
-      this.util.showMessage('Delete is failed: ' + this.util.getErrorMessage(err));
-    });
-  }
 
   /**
    * check is exist
@@ -193,7 +181,7 @@ export class AddValueDialogComponent implements OnInit {
    */
   checkIsExist(ret, cb) {
     this.redisService.call(ret.id, [['EXISTS', ret.key]]).subscribe((r) => {
-      if (r && r.length > 0 && r[0] > 0) { // exist
+      if (!r[0].error && r[0].result > 0) { // exist
         this.dialogService.open(ConfirmDialogComponent, {
           width: '360px', data: {
             title: `Key "${ret.key}" Already Exists`,
@@ -201,7 +189,7 @@ export class AddValueDialogComponent implements OnInit {
           }
         }).afterClosed().subscribe(cr => {
           if (cr) {
-            this.removeExistKey(ret, cb);
+            cb();
           }
         });
       } else {
diff --git a/src/app/components/data-viewer/data-viewer.component.ts b/src/app/components/data-viewer/data-viewer.component.ts
index 7033f54..5ac54bb 100644
--- a/src/app/components/data-viewer/data-viewer.component.ts
+++ b/src/app/components/data-viewer/data-viewer.component.ts
@@ -7,7 +7,7 @@ import _ from 'lodash';
 import {UtilService} from '../../services/util.service';
 import {Observable} from 'rxjs';
 import {Store} from '@ngrx/store';
-import {ReqFetchTree} from '../../ngrx/actions/redis-actions';
+import {ReqFetchTree, RedisConnectFailed} from '../../ngrx/actions/redis-actions';
 
 /**
  * the backend type to frontend type map
@@ -124,7 +124,10 @@ export class DataViewerComponent implements OnInit, OnChanges {
           this.fetchData();
           this.util.showMessage('Deleted successfully.');
           if (cb) { cb(); }
-        }, () => this.util.showMessage('Delete is failed.'));
+        }, () => {
+          this.util.showMessage('Deleted Failed.');
+          this._store.dispatch(new RedisConnectFailed({id: this.pageData.id}))
+        }
       }
     });
   }
@@ -180,7 +183,7 @@ export class DataViewerComponent implements OnInit, OnChanges {
       this.loadingPageData = true;
       this.redisService.call(instanceId, [['LRANGE', key, start, end], ['LLEN', key]]).subscribe(ret => {
           this.page.totalSize = ret[1];
-          this.data = injectValuesToArray(ret[0]);
+          this.data = injectValuesToArray(ret[0].result);
           this.showPagination = true;
           this.loadingPageData = false;
         }
@@ -189,12 +192,13 @@ export class DataViewerComponent implements OnInit, OnChanges {
       this.loadingPageData = true;
       this.redisService.call(instanceId, [['ZRANGE', key, start, end, 'withscores'], ['ZCARD', key]]).subscribe(ret => {
           this.page.totalSize = ret[1];
+          const { result } = ret[0];
           this.data = [];
-          for (let i = 0; i < ret[0].length;) {
+          for (let i = 0; i < result.length;) {
             this.data.push({
               index: this.page.pageIndex * this.page.pageSize + (i / 2),
-              score: parseFloat(ret[0][i + 1]),
-              value: ret[0][i],
+              score: parseFloat(result[i + 1]),
+              value: result[i],
             });
             i += 2;
           }
@@ -206,7 +210,7 @@ export class DataViewerComponent implements OnInit, OnChanges {
       if (!this.setCachedData) {
         this.loadingPageData = true;
         this.redisService.call(instanceId, [['SMEMBERS', key]]).subscribe(ret => {
-          this.setCachedData = injectValuesToArray(ret[0]);
+          this.setCachedData = injectValuesToArray(ret[0].result);
           this.page.totalSize = this.setCachedData.length;
           this.data = this.setCachedData.slice(start, end + 1);
           this.loadingPageData = false;
@@ -222,10 +226,11 @@ export class DataViewerComponent implements OnInit, OnChanges {
         this.loadingPageData = true;
         this.redisService.call(instanceId, [['HGETALL', key]]).subscribe(ret => {
             this.hashCachedData = [];
-            for (let i = 0; i < ret[0].length;) {
+            const { result } = ret[0];
+            for (let i = 0; i < result.length;) {
               this.hashCachedData.push({
-                key: ret[0][i],
-                value: ret[0][i + 1],
+                key: result[i],
+                value: result[i + 1],
               });
               i += 2;
             }
@@ -244,7 +249,7 @@ export class DataViewerComponent implements OnInit, OnChanges {
       this.loadingPageData = true;
       this.redisService.call(instanceId, [['GET', key]]).subscribe(ret => {
         this.loadingPageData = false;
-        this.stringValue = ret[0];
+        this.stringValue = ret[0].result;
       });
     }
   }
@@ -358,8 +363,8 @@ export class DataViewerComponent implements OnInit, OnChanges {
           this.onDeleteValue.emit();
           this._store.dispatch(new ReqFetchTree({id: this.pageData.id}));
         }, e => {
-          this.util.showMessage('Delete is failed.');
-          console.error(e);
+          this.util.showMessage('Delete Failed.');
+          this._store.dispatch(new RedisConnectFailed({id: this.pageData.id}))
         });
       }
     });
diff --git a/src/app/components/import-data-dialog/import-data-dialog.component.ts b/src/app/components/import-data-dialog/import-data-dialog.component.ts
index a92c53b..0dd87ed 100644
--- a/src/app/components/import-data-dialog/import-data-dialog.component.ts
+++ b/src/app/components/import-data-dialog/import-data-dialog.component.ts
@@ -113,10 +113,10 @@ export class ImportDataDialogComponent implements OnInit {
     });
 
     const totalRow = this.flushDB ? commands.length - 1 : commands.length;
-    this.redisService.call(this.instanceId, commands).subscribe((rsp) => {
+    this.redisService.call(this.instanceId, commands).subscribe((results) => {
       let numberOfSucceed = 0;
-      _.each(rsp, v => {
-        numberOfSucceed += (!!v && v.toString().toLowerCase().indexOf('err') < 0) ? 1 : 0;
+      _.each(results, v => {
+        numberOfSucceed += v.error ? 0 : 1;
       });
       numberOfSucceed -= this.flushDB ? 1 : 0;
       const numberOfFailed = totalRow - numberOfSucceed;
diff --git a/src/app/ngrx/effects/cli-effect.ts b/src/app/ngrx/effects/cli-effect.ts
index 56217f0..26a858b 100644
--- a/src/app/ngrx/effects/cli-effect.ts
+++ b/src/app/ngrx/effects/cli-effect.ts
@@ -31,13 +31,17 @@ export class CliEffect {
           action['payload'].redisId,
           [action['payload'].command]).pipe(
           map(ret => {
+            const { error } = ret[0];
+            const result = error ? ret[0].message : ret[0].result;
+
             if (action['payload'].cb) {
-              action['payload'].cb(false);
+              action['payload'].cb(error);
             }
+            
             return new CommandRunFinished({
-              result: ret[0],
+              result,
               id: action['payload'].id,
-              error: !(ret[0] && ret[0].toString() && ret[0].toString().toLowerCase().indexOf('err') < 0),
+              error,
             });
           }),
           catchError((e) => {
diff --git a/src/app/ngrx/effects/page-effect.ts b/src/app/ngrx/effects/page-effect.ts
index fc948c1..8e25208 100644
--- a/src/app/ngrx/effects/page-effect.ts
+++ b/src/app/ngrx/effects/page-effect.ts
@@ -34,26 +34,30 @@ export class PageEffect {
           action['payload'].id,
           [['info']]).pipe(
           map(ret => {
-            const rawInfo = ret[0];
-            const result = [];
-            rawInfo.split('\n').forEach(line => {
-              if (line.indexOf('#') === 0) {
-                return;
-              }
-              if (line.trim() === '') {
-                return;
-              }
-              const parts = line.split(':');
-              result.push({
-                key: parts[0].split('_').join(' '),
-                value: parts[1],
+            if (!ret[0].error) {
+              const rawInfo = ret[0].result;
+              const result = [];
+              rawInfo.split('\n').forEach(line => {
+                if (line.indexOf('#') === 0) {
+                  return;
+                }
+                if (line.trim() === '') {
+                  return;
+                }
+                const parts = line.split(':');
+                result.push({
+                  key: parts[0].split('_').join(' '),
+                  value: parts[1],
+                });
               });
-            });
-            return new LoadedPage({
-              item: result,
-              requestId: action['payload'].requestId,
-              id: action['payload'].id
-            });
+              return new LoadedPage({
+                item: result,
+                requestId: action['payload'].requestId,
+                id: action['payload'].id
+              });
+            } else {
+              this.util.showMessage('Failed to load instance.');
+            }
           }),
           catchError(() => {
             const id = action['payload'].id;