DELETE FROM DR$WAITING

Hi Experts

When perform action on form, there will run below script at background, why?

Is there any impact if not run this script?

DELETE FROM DR$WAITING
WHERE
 WTG_CID = :B2 AND WTG_PID = :B1 AND EXISTS (SELECT 1 FROM DR$PENDING WHERE
  DR$PENDING.PND_CID = DR$WAITING.WTG_CID AND DR$PENDING.PND_PID =
  DR$WAITING.WTG_PID AND DR$PENDING.PND_ROWID = DR$WAITING.WTG_ROWID)

Thanks in advanced

Regards

Fengling