yii\db\oci\Schema::findSchemaNames PHP Method

    protected function findSchemaNames()
    {
        $sql = <<<SQL
SELECT username
  FROM dba_users u
 WHERE EXISTS (
    SELECT 1
      FROM dba_objects o
     WHERE o.owner = u.username )
   AND default_tablespace not in ('SYSTEM','SYSAUX')
SQL;
        return $this->db->createCommand($sql)->queryColumn();
    }