- some members of 'MyTmGxact' is only accessed locally, extract them to local
  variable 'MyTmGxactLocal'
- get rid of gid in MyTmGxact and form it with timestamp and gxid if needed.
- get rid of 'currentGxact' and check 'MyTmGxactLocal->state' to see if the
  distributed transaction is started or not.