WARNING! Physical Log size 50000 is too small ?? Why ? And how to fix it ?

Dear Here, Today,I found following warning in online.log . My database OS is AIX and DB is Informix Database server 7.3. 09:05:45 WARNING! Physical Log size 50000 is too small. Physical Log overflows may occur during peak activity. Recommended minimum Physical Log size is 20 times maximum concurrent user threads. I had config Physical and Logical : # Physical Log Configuration PHYSDBS rootdbs # Location (dbspace) of physical log PHYSFILE 50000 # Physical log file size (Kbytes) # Logical Log Configuration LOGFILES 120 # Number of logical log files LOGSIZE 2000 # Logical log size (Kbytes) Actually , My dbspace in used is 27% and 73% is avaiabled . and concurrent user between 500-600 and each user session size is 7k . So , Physical Log size should be enough . Why this warning happen ? and How to fix it ? PLS Help me !! Thanks. Regards Jerry