rsdb/reco_sync_all_server is a SAP Parameter attribute which is used to control Activation of the Synchronisation of all AppServer during the Database 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 R/3 application servers of a system communicate with each other in
the case that a database reconnent is required from a failed primary
database server to a standby database server. The parameter should be
set to ON in a pure High-Availabilty-Parallel-Databas
e-Server-Installation (all application servers are always only ever
connected to one database server) or during installation uof a standdy
database server accessible using an IP-Address-Switch-Over-Software (
See SAP Parameter Documentation for full SAP documentation for this profile parameter.