dbs/db4/dbsl_trace is a SAP Parameter attribute which is used to control DbSl trace settings. information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
This parameter activates a DBSL trace for SAP on DB2/400. This lets you trace calls to the database. You can find a description in SAP note 395365.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.