The LogLevel directive must be enabled.

The server error logs are invaluable because they can also be used to identify potential problems and enable proactive remediation. Log data can reveal anomalous behavior such as “not found” or “unauthorized” errors that may be an evidence of attack attempts. Failure to enable error logging can significantly reduce the ability of Web Administrators to detect or remediate problems. While the ErrorLog directive configures the error log file name, the LogLevel directive is used to configure the severity level for the error logs. The log level values are the standard syslog levels: emerg, alert, crit, error, warn, notice, info and debug.