PSORT_DBTEMP and DBSPACETEMP

Hi, I am working on INFORMIX ONLINE Dynamic Server. I have come across a problem where when I do a sort using Sequential Scan it blows up during the weekends and sometimes during night time. ( SQL ERR:567 ISAM ERR:28). The PSORT_DBTEMP is pointing to the logical logs directory. When I change it to /tmp, the sort queries work. The manual says using PSORT_DBTEMP will definitely cause this problem. I outputted the disk space in the logical logs directory when the problem happened, and there was plenty of disk space. The manual says to use DBSPACETEMP. I set up DBSPACETEMP as an environmental variable and ran the sort queries but it would still blow up. When I used PSORT_DBTEMP as an environmental variable, setting it to /tmp, the queries work. We had this same problem sometime back when we had our configuration variable PSORT_DBTEMP set to /tmp. Our previous DBA changed it to point to the logical logs directory and it was working fine until recently. Now when we set it to /tmp it seems to work fine. Any ideas, comments on why this is happening would be really helpful. Thanks in advance, Hari TeleServices Resources