rsdb/reco_sosw_for_db is a SAP Parameter attribute which is used to control Activation of a Database-Reconnect feature for Switch Over Software 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 .
ON
The work processes of an application server inform themselves if the
database on the standby database server was restarted. This ensures that
not all work processes contain an error when the primary database server
fails and can reconnect themselves to the standby database server
without any errors. Prerequisite for this is that the standby database
server can be reached using the same IP address (the same IP label) as
the failed primary database server (-> IP address switch over).
OFF
The feature above is not activated. This should be the setting if no
standby database server is installed and no IP address switch over
software is implemented for the database service.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.