In general, applications should handle deletion of log data from a log stream. If the application does not manage deletion, the installation might be able to use the retention period and automatic deletion functions in system logger to manage the amount of log data you keep in each log stream. See Managing log data: How much? For how long? for the retention period and automatic deletion. You can also increase the amount of space available for DASD log data sets using the DSEXTENT parameter in the LOGR couple data set. See Increasing the space available for DASD log data sets.

If for some reason, your installation wants to delete log data, first carefully evaluate the needs of application or applications writing data to the log stream. For some log streams, deleting log data is not a problem, while for others it could be disastrous.