update docu for use of DITTO_LOGGING_TOTAL_LOG_FILE_SIZE in installat…

…ion-operating.md;

Signed-off-by: Stefan Maute <stefan.maute@bosch.io>

documentation/src/main/resources/pages/ditto/installation-operating.md

@@ -241,7 +241,8 @@ Gathering logs for a running Ditto installation can be achieved by:
 
 * writing logs to log files: this can be done by setting the environment variable `DITTO_LOGGING_FILE_APPENDER` to `true`
    * configure the amount of log files, and the total amount of space used for logs files via these environment 
-     variables. It is also possible to clean up old log files and archives at start up:
+     variables. It is also possible to clean up old log files and archives at start up.
+     In case `DITTO_LOGGING_TOTAL_LOG_FILE_SIZE` is used it is necessary to configure also `DITTO_LOGGING_MAX_LOG_FILE_HISTORY_IN_DAYS`.
        * `DITTO_LOGGING_FILE_NAME_PATTERN` (default: /var/log/ditto/<service-name>.log.%d{yyyy-MM-dd}.gz)
        * `DITTO_LOGGING_MAX_LOG_FILE_HISTORY_IN_DAYS` (default: 10) 
        * `DITTO_LOGGING_TOTAL_LOG_FILE_SIZE` (default: 1GB)