Re-create Index on a Large Table

Hi Everyone, I have a table with 450,000 records inserted via an ESQL/C program. Since the transaction rate started to go down when the number of records approached 300,000 and running update statistics took a long time and did not seem to help much, I tried to drop and re-created the one and only primary index on the table and went into a worse situation. After I invoked dbaccess to run the drop and create index SQL file, I saw "Killed" appeared on my console. After that the host was not accessible by any command, only returns "The fork function failed. There is not enough memory available". So my system administrator re-booted the box. I am running AIX 3.2.5, Informix 7.10. The index takes about 22 MB disk space at that time and I have 20 MB virtual memory and 35 MB disk space for DBSPACETEMP in server configuration. There is no error message reported in Informix server log. As far as I know drop and create an index uses DBSPACETEMP and virtual portion of shared memory. I guess something went beyond at O.S. level. Please shed some lights. Any info. is greately appreciated !