1st question is: is the DBSPACETEMP parameter specified in your ONCONFIG file?
If not, temp space with be prempted in rootdbs, which may explain why your issue uses to occur.
So you can specify one or several temp dbspaces for DBSPACETEMP onconfig parameter.
The other solution is to create a temp dbspace and specify it in the DBSPACETEMP environment variable.
You can create temp dbspaces as much as you wish, and can drop them as long as the temp dbspace is no more in use