The log files are stored in the run directory. The directory is specified with the general database parameter RUNDIRECTORY and created by the database system when installing a new database instance.
The default value for the run directory is <independent_data_path>/wrk/<database_name>
The log files in the run directory are overwritten at a restart after a database crash. Older log files are therefore moved to the directory <diag_history_path>. The default value for this directory is <rundirectory>/DIAGHISTORY.
See also SAP DB Directories