system/Database/BaseConnection.php
public function transStart(bool $test_mode = false): bool
	{
		if (! $this->transEnabled)
		{
			return false;
		}

		return $this->transBegin($test_mode);
	}
public function transStart(bool $test_mode = false): bool
	{
		if (! $this->transEnabled)
		{
			return false;
		}

		return $this->transBegin($test_mode);
	}
Start Transaction

@param  boolean $test_mode = FALSE
@return boolean