diff --git a/pandora_server/lib/PandoraFMS/Config.pm b/pandora_server/lib/PandoraFMS/Config.pm
index 718b3e6b60..f9b86637b0 100644
--- a/pandora_server/lib/PandoraFMS/Config.pm
+++ b/pandora_server/lib/PandoraFMS/Config.pm
@@ -304,6 +304,7 @@ sub pandora_load_config {
 	$pa_config->{'openstreetmaps_description'} = 0;
 	$pa_config->{"eventserver"} = 1; # 4.0
 	$pa_config->{"correlationserver"} = 1; # 757
+	$pa_config->{"correlation_threshold"} = 30; # 757
 	$pa_config->{"event_window"} = 3600; # 4.0
 	$pa_config->{"log_window"} = 3600; # 7.741
 	$pa_config->{"elastic_query_size"} = 10; # 7.754 Elements per request (ELK)
@@ -791,6 +792,9 @@ sub pandora_load_config {
 		elsif ($parametro =~ m/^correlationserver\s+([0-9]*)/i) {
 			$pa_config->{'correlationserver'}= clean_blank($1);
 		}
+		elsif ($parametro =~ m/^correlation_threshold\s+([0-9]*)/i) {
+			$pa_config->{'correlation_threshold'}= clean_blank($1);
+		}
 		elsif ($parametro =~ m/^icmpserver\s+([0-9]*)/i) {
 			$pa_config->{'icmpserver'}= clean_blank($1);
 		}
diff --git a/pandora_server/lib/PandoraFMS/Core.pm b/pandora_server/lib/PandoraFMS/Core.pm
index 6f4e16e9fe..7bfcd5ce35 100644
--- a/pandora_server/lib/PandoraFMS/Core.pm
+++ b/pandora_server/lib/PandoraFMS/Core.pm
@@ -278,7 +278,31 @@ our @EXPORT = qw(
 
 # Some global variables
 our @DayNames = qw(sunday monday tuesday wednesday thursday friday saturday);
-our @ServerTypes = qw (dataserver networkserver snmpconsole reconserver pluginserver predictionserver wmiserver exportserver inventoryserver webserver eventserver icmpserver snmpserver satelliteserver transactionalserver mfserver syncserver wuxserver syslogserver provisioningserver migrationserver);
+our @ServerTypes = qw (
+	dataserver
+	networkserver
+	snmpconsole
+	reconserver
+	pluginserver
+	predictionserver
+	wmiserver
+	exportserver
+	inventoryserver
+	webserver
+	eventserver
+	icmpserver
+	snmpserver
+	satelliteserver
+	transactionalserver
+	mfserver
+	syncserver
+	wuxserver
+	syslogserver
+	provisioningserver
+	migrationserver
+	alertserver
+	correlationserver
+);
 our @AlertStatus = ('Execute the alert', 'Do not execute the alert', 'Do not execute the alert, but increment its internal counter', 'Cease the alert', 'Recover the alert', 'Reset internal counter');
 
 # Event storm protection (no alerts or events)
@@ -624,19 +648,33 @@ sub pandora_evaluate_alert ($$$$$$$;$$$$) {
 	}
 	# Correlated alert
 	else {
-		my $rc = enterprise_hook (
-			'evaluate_correlated_alert',
-			[
-				$pa_config,
-				$dbh,
-				$alert,
-				$correlatedItems,
-				$event,
-				$log
-			]
-		);
+		if (defined($data)) {
+			# Data contains the number of occurrences of correlated alert.
+			if ($data < $alert->{'pool_occurrences'}) {
+				# Less occurrences than previous execution, recovered.
+				# 4 Recover the alert
+				return 4;
+			} elsif ($data eq $alert->{'pool_occurrences'}) {
+				# Same occurrences as previous execution, nothing new, but present in pool.
+				# 1 Do not execute the alert.
+				return 1;
+			}
 
-		return $status unless (defined ($rc) && $rc == 1);
+		} else {
+			my $rc = enterprise_hook (
+				'evaluate_correlated_alert',
+				[
+					$pa_config,
+					$dbh,
+					$alert,
+					$correlatedItems,
+					$event,
+					$log
+				]
+			);
+
+			return $status unless (defined ($rc) && $rc == 1);
+		}
 	}
 	
 	# Check min and max alert limits
diff --git a/pandora_server/lib/PandoraFMS/DB.pm b/pandora_server/lib/PandoraFMS/DB.pm
index 1f53cb228b..26d8338f17 100644
--- a/pandora_server/lib/PandoraFMS/DB.pm
+++ b/pandora_server/lib/PandoraFMS/DB.pm
@@ -917,7 +917,7 @@ sub get_db_value_limit ($$$;@) {
 
 ##########################################################################
 ## Get a single row returned by an SQL query as a hash reference. Returns
-## -1 on error.
+## hash or undef on error.
 ##########################################################################
 sub get_db_single_row ($$;@) {
 	my ($dbh, $query, @values) = @_;
diff --git a/pandora_server/lib/PandoraFMS/Tools.pm b/pandora_server/lib/PandoraFMS/Tools.pm
index 7fcca66b85..1e489fb084 100755
--- a/pandora_server/lib/PandoraFMS/Tools.pm
+++ b/pandora_server/lib/PandoraFMS/Tools.pm
@@ -2524,6 +2524,7 @@ sub get_server_name {
 	return "PROVISIONINGSERVER" if ($server_type eq PROVISIONINGSERVER);
 	return "MIGRATIONSERVER" if ($server_type eq MIGRATIONSERVER);
 	return "ALERTSERVER" if ($server_type eq ALERTSERVER);
+	return "CORRELATIONSERVER" if ($server_type eq CORRELATIONSERVER);
 
 	return "UNKNOWN";
 }