# Control Update ### Control Update The control file is a file that is updated in real time to assure the integrity of all files managed by the file server. There are only two cases when you will need to make a Control Update: **When restoring a new database into an existing system.** If you restore data files from another system, the control file from the source system will never be the same as the control file from the target system. You can perform a control update without any worries. **After a Day Rebuilder** If for any reasons you experience problems with the file server (hard disk failure, electricity, …), you might need to run the Day Rebuilder program to recreate all transactions that were done for the current day. If the program failed to recreate all transactions, the system will not restart and you will get a control file error. If the system shows you that the check number from the CONTROL file on the left is LOWER then the system's ACTUAL last check number on the right, you can perform a control update without any worries either. {% hint style="danger" %} WARNING: If the system shows you that the check number from the CONTROL file on the left is HIGHER then the system's ACTUAL last check number on the right, and you perform a control update at that point, you will loose the last checks that were done. Before going ahead, you should try to run the Day Rebuilder option using the second backup. The control update can only be performed using the Distributor password. Once you perform a control update, there is no turning back. Be careful when using this option and if there is any doubt, call the Maitre'D support team. {% endhint %} The Z number is the number of times that the End of day was run on the file server. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.payfacto.com/payfacto-knowledge/maitred-pos/maitred/maitred-online-help-contents-by-module/server-control/tools/control-update.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.