diff --git a/application/ui.linkswidget.class.inc.php b/application/ui.linkswidget.class.inc.php
index 1f4e63da5..e2bf70609 100644
--- a/application/ui.linkswidget.class.inc.php
+++ b/application/ui.linkswidget.class.inc.php
@@ -100,15 +100,18 @@ class UILinksWidget
 	 * @param array $aArgs Extra context arguments
 	 * @param DBObject $oCurrentObj The object to which all the elements of the linked set refer to
 	 * @param int $iUniqueId A unique identifier of new links
-	 * @param boolean $bReadOnly Display link as editable or read-only. Default is false (editable)
+	 * @param bool $bReadOnly Display link as editable or read-only. Default is false (editable)
+	 * @param bool $bAllowRemoteExtKeyEdit If true, the ext. key to the remote object can be edited, otherwise it will be read-only
 	 *
 	 * @return array The HTML fragment of the one-row form
 	 * @throws \ArchivedObjectException
 	 * @throws \CoreException
 	 * @throws \CoreUnexpectedValue
 	 * @throws \Exception
+	 *
+	 * @since 3.1.0 3.0.4 3.0.3-1 N°6124 - Workaround performance problem on the modification of an object with an n:n relation having a large volume
 	 */
-	protected function GetFormRow(WebPage $oP, DBObject $oLinkedObj, $linkObjOrId, $aArgs, $oCurrentObj, $iUniqueId, $bReadOnly = false)
+	protected function GetFormRow(WebPage $oP, DBObject $oLinkedObj, $linkObjOrId, $aArgs, $oCurrentObj, $iUniqueId, $bReadOnly = false, $bAllowRemoteExtKeyEdit = true)
 	{
 		$sPrefix = "$this->m_sAttCode{$this->m_sNameSuffix}";
 		$aRow = array();
@@ -139,8 +142,11 @@ class UILinksWidget
 				$aRow['form::checkbox'] = "<input class=\"selection\" data-remote-id=\"$iRemoteObjKey\" data-link-id=\"$iKey\" data-unique-id=\"$iUniqueId\" type=\"checkbox\" onClick=\"oWidget".$this->m_iInputId.".OnSelectChange();\" value=\"$iKey\">";
 				foreach ($this->m_aEditableFields as $sFieldCode)
 				{
+					// N°6124 - Force remote ext. key as read-only if too many items in the linkset
+					$bReadOnlyField = ($sFieldCode === $this->m_sExtKeyToRemote) && (false === $bAllowRemoteExtKeyEdit);
+
 					$sSafeFieldId = $this->GetFieldId($linkObjOrId->GetKey(), $sFieldCode);
-					$this->AddRowForFieldCode($aRow, $sFieldCode, $aArgs, $linkObjOrId, $oP, $sNameSuffix, $sSafeFieldId);
+					$this->AddRowForFieldCode($aRow, $sFieldCode, $aArgs, $linkObjOrId, $oP, $sNameSuffix, $sSafeFieldId, $bReadOnlyField);
 					$aFieldsMap[$sFieldCode] = $sSafeFieldId;
 				}
 			}
@@ -255,11 +261,24 @@ JS
 		return $aRow;
 	}
 
-	private function AddRowForFieldCode(&$aRow, $sFieldCode, &$aArgs, $oLnk, $oP, $sNameSuffix, $sSafeFieldId): void
+	/**
+	 * @param $aRow
+	 * @param $sFieldCode
+	 * @param $aArgs
+	 * @param $oLnk
+	 * @param $oP
+	 * @param $sNameSuffix
+	 * @param $sSafeFieldId
+	 * @param bool $bReadOnlyField If true, the field will be read-only, otherwise it can be edited
+	 *
+	 * @return void
+	 * @since 3.1.0 3.0.4 3.0.3-1 N°6124 - Workaround performance problem on the modification of an object with an n:n relation having a large volume
+	 */
+	private function AddRowForFieldCode(&$aRow, $sFieldCode, &$aArgs, $oLnk, $oP, $sNameSuffix, $sSafeFieldId, $bReadOnlyField = false): void
 	{
 		if (($sFieldCode === $this->m_sExtKeyToRemote))
 		{
-			// current field is the lnk extkey to the remote class
+			// Current field is the lnk extkey to the remote class
 			$aArgs['replaceDependenciesByRemoteClassFields'] = true;
 			$sRowFieldCode = 'static::key';
 			$aArgs['wizHelperRemote'] = $aArgs['wizHelper'].'_remote';
@@ -281,20 +300,31 @@ JS
 		$sDisplayValue = $oLnk->GetEditValue($sFieldCode);
 		$oAttDef = MetaModel::GetAttributeDef($this->m_sLinkedClass, $sFieldCode);
 
-		$aRow[$sRowFieldCode] = '<div class="field_container" style="border:none;"><div class="field_data"><div class="field_value">'
-			.cmdbAbstractObject::GetFormElementForField(
-				$oP,
-				$this->m_sLinkedClass,
-				$sFieldCode,
-				$oAttDef,
-				$sValue,
-				$sDisplayValue,
-				$sSafeFieldId,
-				$sNameSuffix,
-				0,
-				$aArgs
-			)
-			.'</div></div></div>';
+		if ($bReadOnlyField) {
+			$sFieldForHtml = $sDisplayValue;
+		} else {
+			$sFieldForHtml = cmdbAbstractObject::GetFormElementForField(
+					$oP,
+					$this->m_sLinkedClass,
+					$sFieldCode,
+					$oAttDef,
+					$sValue,
+					$sDisplayValue,
+					$sSafeFieldId,
+					$sNameSuffix,
+					0,
+					$aArgs
+				);
+		}
+
+		$aRow[$sRowFieldCode] = <<<HTML
+<div class="field_container" style="border:none;">
+	<div class="field_data">
+		<div class="field_value">$sFieldForHtml</div>
+	</div>
+</div>
+HTML
+		;
 	}
 
 	private function GetFieldId($iLnkId, $sFieldCode, $bSafe = true)
@@ -374,6 +404,7 @@ JS
 		$oBlock->sRemoteClass = $this->m_sRemoteClass;
 
 		$oValue->Rewind();
+		$bAllowRemoteExtKeyEdit = $oValue->Count() <= utils::GetConfig()->Get('link_set_max_edit_ext_key');
 		$aForm = array();
 		$iMaxAddedId = 0;
 		$iAddedId = -1; // Unique id for new links
@@ -398,7 +429,7 @@ JS
 			}
 
 			$iMaxAddedId = max($iMaxAddedId, $key);
-			$aForm[$key] = $this->GetFormRow($oPage, $oLinkedObj, $oCurrentLink, $aArgs, $oCurrentObj, $key, $bReadOnly);
+			$aForm[$key] = $this->GetFormRow($oPage, $oLinkedObj, $oCurrentLink, $aArgs, $oCurrentObj, $key, $bReadOnly, $bAllowRemoteExtKeyEdit);
 		}
 		$oBlock->iMaxAddedId = (int) $iMaxAddedId;
 
diff --git a/core/config.class.inc.php b/core/config.class.inc.php
index 2894cf4a6..13e1c33d8 100644
--- a/core/config.class.inc.php
+++ b/core/config.class.inc.php
@@ -480,6 +480,14 @@ class Config
 			'source_of_value' => '',
 			'show_in_conf_sample' => true,
 		],
+		'link_set_max_edit_ext_key' => [
+			'type'                => 'integer',
+			'description'         => 'Maximum number of items in the link that allow editing the remote external key. Above that limit, remote external key cannot be edited. Mind that setting this limit too high can have a negative impact on performances.',
+			'default'             => 50,
+			'value'               => 50,
+			'source_of_value'     => '',
+			'show_in_conf_sample' => true,
+		],
 		'tag_set_item_separator' => [
 			'type' => 'string',
 			'description' => 'Tag set from string: tag label separator',