diff --git a/MarketPlaces/DB_Connection/db_connection.py b/MarketPlaces/DB_Connection/db_connection.py
index 46c05cd..03de3d2 100644
--- a/MarketPlaces/DB_Connection/db_connection.py
+++ b/MarketPlaces/DB_Connection/db_connection.py
@@ -29,6 +29,8 @@ def verifyMarketPlace(cur, nameMarket):
 
     try:
 
+        cur.execute("lock table marketPlaces IN ACCESS EXCLUSIVE MODE")
+
         cur.execute("select market_id from marketPlaces where name_market = %(nameMarket)s limit 1", {'nameMarket': nameMarket})
 
         recset = cur.fetchall()
@@ -48,6 +50,8 @@ def verifyVendor(cur, nameVendor, marketId):
 
     try:
 
+        cur.execute("lock table vendors IN ACCESS EXCLUSIVE MODE")
+
         cur.execute("select vendor_id from vendors where name_vendor = %(nameVendor)s and market_id = %(marketId)s "
                     "limit 1", {'nameVendor': nameVendor, 'marketId': marketId})
 
@@ -67,6 +71,8 @@ def verifyItem(cur, marketId, vendorId, nameItem):
 
     try:
 
+        cur.execute("lock table items IN ACCESS EXCLUSIVE MODE")
+
         cur.execute("select item_id from items where market_id = %(marketId)s and vendor_id = %(vendorId)s and name_item = %(nameItem)s"
                     "limit 1", {'marketId': marketId, 'vendorId': vendorId, 'nameItem': nameItem})