Answer
First check the actual log content for genuine recurring errors before assuming it's simply excessive normal logging — persistent errors filling the logs might need their own separate investigation. If the logs are otherwise clean, configure proper log rotation and an appropriate log level through the Middleware Server Admin Console, under Main Cluster > Managed Servers > MWS Logging: set a 'Limit Number of Retained Files' value to cap how many historical log files are allowed to accumulate, and set the log level to an appropriately conservative level, commonly Warning, rather than a more verbose default. This addresses the log growth at its source, rather than continuing to rely on manual periodic cleanup of old log files.