Re: Why long transaction cannot rollback?????

Madeline Wu wrote: > > There are two IBM RS/6000. The model are 370 and 380. > They are all installed Informix On-line 5.0. The dbspaces > are same. Only Share-Memory differ in Max User#. There > are 12 logical logs. Every log is 1,024Kb. In 380, the long > transaction can rollback. But 370 cannot. Now LTXHWM > =50,LTXEHWM=60. When a log tansaction happened, > the 12 logical logs are 100% used. Informix is holded on > there, cannot work anymore. The message log showed " > logical logs are full, Need to Backup." I used Auto-Backup, > but cannot backup, and still cannot work. Check the user > flag C-R-----, the mean is wait for a checkpoint and process > a rollback. Why cannot rollback totally??? When I changed > the LTXHWM=80, LTXEHWM=90, the same thing was > happened. When I changed LTXHWM=10, LTXEHWM=30, > only 2 logs full, the long transaction was happened, and > rollback totally. But only 2 logs is too short!!! What happened??? > What should I do to let it work normally??? > > Madeline Wu from Taiwan.... A long transaction is produced when it's executing one atomic operation over the B.D, and the space in the logical logs it isn't enough for finish this transaction. The tbconfig limit LTXHWM and LTXEHWM are used by Informix to check at which % of ocupation of logicals logs Informix thinks the long transaction happened. (One limit is a soft limit and the other one is a hard limit). When you changed the limits to 10 and 30, Informix understand that at 30% of ocupation of logical logs there is a long transaction, and in this case the rollback was ok because there was about 10 logical logs frees to do the rollback. You have to notice to complete the rollback Informix uses the logical logs which are free. Other thing, when it happens one checkpoint, the logical log where the checkpoint happened, it is not freed until : 1- The trasaction implied in this logical log finished 2- Other checkpoint happens other time There was another condition that I dont remember well, but in the Administrator Manual of Informix On-Line all of things are very good explained. I hope my explication help you.