memory allocation issues

hi i use db_dataobject with html_quickform in my application. lately i realized, that memory exhaustion problem seems to show a little bit to often. on my mashine i have memory limit set to 8mb, appliation is rather medicore-complicated, but it does quite a lot of db queries (with help of dataobjects), but size of data transfered isn`t really big (some hundreds bytes per query). when there is a lot of queries php hangs because of memory limit. if found that it happens in PEAR.php - in line with call to debug_backtrace. i want to locate the problem, because it doesn`t seem that this error occurs when i turn off this backtrace call - so it`s not that application is running really low on memory with its normal work. i would like to know your opinion about this problem, where should i look for the cause? - db class misses some post-query clean up? - db_dataobjects misses - || - ? - debug_bactrace does some really complicated work with memory before it produces return value? - php memory manager sleeps to much before automatic clean up? (connected with 2 first points from above) i know i could raise the memory limit, but i think that it maybe can be fixed without it - i find php a little bit to wasteful with memory, maybe complicated scripts (like pear classes) should do their own unset`s? rash