diff --git a/google/cloud/sql/v1beta4/cloud_sql_resources.proto b/google/cloud/sql/v1beta4/cloud_sql_resources.proto
index 09cd2475cc99e..a6060793e890f 100644
--- a/google/cloud/sql/v1beta4/cloud_sql_resources.proto
+++ b/google/cloud/sql/v1beta4/cloud_sql_resources.proto
@@ -1276,6 +1276,15 @@ message SqlExternalSyncSettingError {
 
     // Final parallel level that is used to do migration.
     PG_SYNC_PARALLEL_LEVEL = 42;
+
+    // The disk size of the replica instance is smaller than the data size of
+    // the source instance.
+    INSUFFICIENT_DISK_SIZE = 43;
+
+    // The data size of the source instance is greater than 1 TB, the number of
+    // cores of the replica instance is less than 8, and the memory of the
+    // replica is less than 32 GB.
+    INSUFFICIENT_MACHINE_TIER = 44;
   }
 
   // Can be `sql#externalSyncSettingError` or