hi, i want to kill a long transaction. that's it the transaction has statu ---P-S, and it cannot be killed with onmode -Z command. please help. i've restarteä informix server and informix client, but the transaction is still here.

The transaction is doing a rollback. You can't kill that...

2 months ago i killed that kind of transaction, with a tool given to me, by informix support. but this tool comes with some parameters that i dont understand. this tool is called tbzero_V73, and i run it with parameters -ark 15

You are NOT supposed to have these kind of tools.
These tools are used for SYSTEM DOWNs! When there is no more way out.
Normally when you kill a transaction, it's supposed to rollback everything it did. Otherwise you'd have a corrupted database.
What support team gave you this tool? If you want to use this tool, I'd suggest you call support.

i only want to find a way, to resolve this kind of problems easily...

Since you have had this problem before you may want to modify the following onconfig parameters - LTXHWM, LTXEHWM and LBU_PRESERVE.

Also, I would identify why this happens - is there a design issue with the application ...

ok, thanks. the parameters are:
LTXHWM 35
LTXEHWM 45
LBU_PRESERVE 1

what values i should give to this variables?