Use the Server Config utility to change the path:
Select Start/Programs/Sybase/Server Config.
Click the Adaptive Server icon from the Products box in the Configure Sybase Servers dialog box.
Click the Configure Adaptive Server button in the Adaptive Server Enterprise box.
Select the name of the server to configure in the Existing Servers box, and click Continue.
Type the login name and password of an Adaptive Server user with System Administrator privileges in the Enter System Administrator Password dialog box.
Click Yes if Adaptive Server is not running, and Server Config prompts you to start it.
Click the Error Log Path button in the Configure Adaptive Serve Enterprise dialog box.
Server Config displays the Error Log Installation Path dialog box.
Type the full path name to an error log file that is not on a network drive, and click OK.
In the Configure Adaptive Server dialog box, click Save to save the new error log setting.
Click Exit to quit Server Config.