diff --git a/InstructorsAndTrainees/connectorToServer/connectortoserver_AnswerQueryToDB.cpp b/InstructorsAndTrainees/connectorToServer/connectortoserver_AnswerQueryToDB.cpp
index 7933900..d89586c 100644
--- a/InstructorsAndTrainees/connectorToServer/connectortoserver_AnswerQueryToDB.cpp
+++ b/InstructorsAndTrainees/connectorToServer/connectortoserver_AnswerQueryToDB.cpp
@@ -2,7 +2,9 @@
 
 void ConnectorToServer::slot_AnswerQueryToDB_ListInstructors(QList<Instructor> listInstructors)
 {
+    //mtxAccess.lock();
     this->listInstructors = listInstructors;
+
     emit signal_UpdateDB(true, false);
 
     QList<User> listUsers;
@@ -10,6 +12,8 @@ void ConnectorToServer::slot_AnswerQueryToDB_ListInstructors(QList<Instructor> l
     {
         listUsers.append(instructor);
     }
+    //mtxAccess.unlock();
+
     emit signal_reInitMessangerByUsers(listUsers);
 }
 
diff --git a/InstructorsAndTrainees/connectorToServer/connectortoserver_LocalModelDB.cpp b/InstructorsAndTrainees/connectorToServer/connectortoserver_LocalModelDB.cpp
index c0fff20..cdec6fe 100644
--- a/InstructorsAndTrainees/connectorToServer/connectortoserver_LocalModelDB.cpp
+++ b/InstructorsAndTrainees/connectorToServer/connectortoserver_LocalModelDB.cpp
@@ -8,36 +8,44 @@ QByteArray ConnectorToServer::getListTaskFimArray()
 
 QByteArray ConnectorToServer::getListTaskAmmArray()
 {
+    QMutexLocker locker(&mtxAccess);
     return listTaskAmmArray;
 }
 
 QList<Instructor> ConnectorToServer::getListInstructors()
 {
+    QMutexLocker locker(&mtxAccess);
     return listInstructors;
 }
 
 QList<Trainee> ConnectorToServer::getListTrainees()
 {
+    QMutexLocker locker(&mtxAccess);
     return listTrainees;
 }
 
 QList<Group> ConnectorToServer::getListGroups()
 {
+    QMutexLocker locker(&mtxAccess);
     return listGroups;
 }
 
 QList<Computer> ConnectorToServer::getListComputers()
 {
+    QMutexLocker locker(&mtxAccess);
     return  listComputers;
 }
 
 QList<Classroom> ConnectorToServer::getListClassrooms()
 {
+    QMutexLocker locker(&mtxAccess);
     return listClassrooms;
 }
 
 QList<TaskAmmFim> ConnectorToServer::getListTasksAMMforTrainee(int trainee_id)
 {
+    QMutexLocker locker(&mtxAccess);
+
     if(mapTasksAMM.contains(trainee_id))
         return mapTasksAMM.value(trainee_id);
     else
@@ -46,6 +54,8 @@ QList<TaskAmmFim> ConnectorToServer::getListTasksAMMforTrainee(int trainee_id)
 
 QList<TaskAmmFim> ConnectorToServer::getListTasksFIMforTrainee(int trainee_id)
 {
+    QMutexLocker locker(&mtxAccess);
+
     if(mapTasksFIM.contains(trainee_id))
         return mapTasksFIM.value(trainee_id);
     else
@@ -54,6 +64,8 @@ QList<TaskAmmFim> ConnectorToServer::getListTasksFIMforTrainee(int trainee_id)
 
 int ConnectorToServer::getCountTasksAMMforTrainee(int trainee_id)
 {
+    QMutexLocker locker(&mtxAccess);
+
     if(mapTasksAMM.contains(trainee_id))
         return mapTasksAMM.value(trainee_id).count();
     else
@@ -62,6 +74,8 @@ int ConnectorToServer::getCountTasksAMMforTrainee(int trainee_id)
 
 int ConnectorToServer::getCountTasksFIMforTrainee(int trainee_id)
 {
+    QMutexLocker locker(&mtxAccess);
+
     if(mapTasksFIM.contains(trainee_id))
         return mapTasksFIM.value(trainee_id).count();
     else
@@ -70,6 +84,8 @@ int ConnectorToServer::getCountTasksFIMforTrainee(int trainee_id)
 
 bool ConnectorToServer::isArchivedInstructor(int id)
 {
+    QMutexLocker locker(&mtxAccess);
+
     for(Instructor instructor : listInstructors)
     {
         if(instructor.getID() == id)
@@ -83,6 +99,8 @@ bool ConnectorToServer::isArchivedInstructor(int id)
 
 bool ConnectorToServer::isAdminInstructor(int id)
 {
+    QMutexLocker locker(&mtxAccess);
+
     for(Instructor instructor : listInstructors)
     {
         if(instructor.getID() == id)
@@ -96,6 +114,8 @@ bool ConnectorToServer::isAdminInstructor(int id)
 
 bool ConnectorToServer::isLoggedInInstructor(int id)
 {
+    QMutexLocker locker(&mtxAccess);
+
     for(Instructor instructor : listInstructors)
     {
         if(instructor.getID() == id)
@@ -109,6 +129,8 @@ bool ConnectorToServer::isLoggedInInstructor(int id)
 
 Instructor ConnectorToServer::getInstructor(int id)
 {
+    QMutexLocker locker(&mtxAccess);
+
     for(Instructor instructor : listInstructors)
     {
         if(instructor.getID() == id)
@@ -119,6 +141,8 @@ Instructor ConnectorToServer::getInstructor(int id)
 
 QList<Trainee> ConnectorToServer::getListTraineesInGroup(int id)
 {
+    QMutexLocker locker(&mtxAccess);
+
     QList<Trainee> list;
     for(Trainee trainee : listTrainees)
     {
@@ -130,6 +154,8 @@ QList<Trainee> ConnectorToServer::getListTraineesInGroup(int id)
 
 bool ConnectorToServer::isArchivedTrainee(int id)
 {
+    QMutexLocker locker(&mtxAccess);
+
     for(Trainee trainee : listTrainees)
     {
         if(trainee.getID() == id)
@@ -143,6 +169,8 @@ bool ConnectorToServer::isArchivedTrainee(int id)
 
 bool ConnectorToServer::isLoggedInTrainee(int id)
 {
+    QMutexLocker locker(&mtxAccess);
+
     for(Trainee trainee : listTrainees)
     {
         if(trainee.getID() == id)
@@ -156,6 +184,8 @@ bool ConnectorToServer::isLoggedInTrainee(int id)
 
 Trainee ConnectorToServer::getTrainee(int id)
 {
+    QMutexLocker locker(&mtxAccess);
+
     for(Trainee trainee : listTrainees)
     {
         if(trainee.getID() == id)
@@ -166,6 +196,8 @@ Trainee ConnectorToServer::getTrainee(int id)
 
 Group ConnectorToServer::getGroup(int id)
 {
+    QMutexLocker locker(&mtxAccess);
+
     for(Group group : listGroups)
     {
         if(group.getID() == id)
@@ -176,6 +208,8 @@ Group ConnectorToServer::getGroup(int id)
 
 int ConnectorToServer::getIdTraineeByLogin(QString login)
 {
+    QMutexLocker locker(&mtxAccess);
+
     for(Trainee trainee : listTrainees)
     {
         if(trainee.getLogin() == login)
@@ -186,6 +220,8 @@ int ConnectorToServer::getIdTraineeByLogin(QString login)
 
 int ConnectorToServer::getIdInstructorByLogin(QString login)
 {
+    QMutexLocker locker(&mtxAccess);
+
     for(Instructor instructor : listInstructors)
     {
         if(instructor.getLogin() == login)
@@ -196,6 +232,8 @@ int ConnectorToServer::getIdInstructorByLogin(QString login)
 
 void ConnectorToServer::clearListModelDB()
 {
+    QMutexLocker locker(&mtxAccess);
+
     listInstructors.clear();
     listGroups.clear();
     listTrainees.clear();