dbs/db4/driver_type is a SAP Parameter attribute which is used to control Database driver type used by DBSL 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 .
Choose the database driver (XDN or XDA). For more information, see SAP
The currently active driver is visible in the developer trace (SM50),
See SAP Parameter Documentation for full SAP documentation for this profile parameter.