I download oci8.c from http://cvs.php.net.(#8573)
I test a follow script again after recompile php.

 * script :
<?php
    $conn = OCILogon("scott","tiger");
    if(!$conn) {
        echo "ocilogon1 error\n\n";
        exit;
    }

    $query  = "select userno from chkuser ";
    $query  .= " where kname = 'test' ";

    $stmt = OCIParse($conn,$query);
    OCIExecute($stmt);
    OCIFetchInto($stmt,$CHKUSER,OCI_ASSOC);
    $usernum = $CHKUSER["USERNO"];

    OCIFreeStatement($stmt);

    OCILogoff($conn);
    echo $usernum." --test break1 \n";
?>

 But this script still use a lot of system memory. when
a large number of user access this script, the httpd is running extremely wierd exactly heap size not a small memory-leak.

 * command for checking memory : 
  ps -ef -o pid -o vsz -o rss -o fname -o args | grep httpd | sort

Before : 
 6384 10704 1800 libhttpd /H2K/HiTEL2000/webservice/apache/bin/httpd
 6385 10704 1776 libhttpd /H2K/HiTEL2000/webservice/apache/bin/httpd
 6386 10704 1776 libhttpd /H2K/HiTEL2000/webservice/apache/bin/httpd
 6387 10704 1776 libhttpd /H2K/HiTEL2000/webservice/apache/bin/httpd
 6388 10704 1776 libhttpd /H2K/HiTEL2000/webservice/apache/bin/httpd
 6395  976  864 grep     grep httpd
27855 10704 4168 libhttpd /H2K/HiTEL2000/webservice/apache/bin/httpd

After just refreshing browser tweenty times : 
 6384 10920 6400 libhttpd /H2K/HiTEL2000/webservice/apache/bin/httpd
 6385 10912 6392 libhttpd /H2K/HiTEL2000/webservice/apache/bin/httpd
 6386 10704 1800 libhttpd /H2K/HiTEL2000/webservice/apache/bin/httpd
 6387 10704 1776 libhttpd /H2K/HiTEL2000/webservice/apache/bin/httpd
 6388 10704 1776 libhttpd /H2K/HiTEL2000/webservice/apache/bin/httpd
 6419 10712 1784 libhttpd /H2K/HiTEL2000/webservice/apache/bin/httpd


Please help !!!