My problem is toolkit request failed. My web application (PHP) run on Zend server 9 IBMi and using toolkit (version 1.6) to call RPG for update process backed , program working fine for a month until last week I found sometimes toolkit didn't call RPG and toolkit.log show like these 30 Jun 2017 21:20:16.281636 Toolkit request failed. Review the database code and message. Database code (if any): 'HY021'. Message: Error occurred in SQL Call Level Interface My error is different from another post in this forum "Toolkit request failed. Possible reason: a CCSID not matching that of system, or updated PTFs may be required. Database code (if any): HY021. Message: Error occurred in SQL Call Level Interface" I fix this problem by restart Zend Server subsystem and Apache server. After restart tooklit request fail gone away but this problem is occurred again in a few hour later. My temporary solution is to restart Zend Server and Apache server every time when found log toolkit request failed. I don't know how to fix it . Please help me find the permanent solution. Thank you in advance.