ORACLE 8 randomly unsucessful execution

Hi! We encounter a weird problem here: from time to time, after a up-time of one week for instance, the PHP pages cannot execute some PL/SQL stored procedures (most of the time it works, but sometimes it doesn't). We solve the problem by restarting Apache, but having no idea of where the problem comes from ... Any idea? Ludo. ---- Here is ou PHP configure script: ./configure \ --with-oracle=/home/oracle/u01/app/oracle/product/8.1.6 \ --with-oci8=/home/oracle/u01/app/oracle/product/8.1.6 \ --with-apache=/usr/local/apache \ --enable-curl \ --enable-track-vars \ --disable-debug \ --without-gd \ --without-mysql \ --enable-sigchild And this is our Apache one: ./configure \ --prefix=/usr/local/apache \ --activate-module=src/modules/php4/libphp4.a \ --enable-module=rewrite \ --enable-rule=SHARED_CORE \ --enable-module=so