rspo/devinit/datafile is a SAP Parameter attribute which is used to control Pathname for file containing device initialization 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 describes a template for generating a file name. For this
+ characters are successively replaced by a name specified in a
formatting action using the command \F<(><<)>Name>. This command can
only be used at the end of the initialization action. The content of the
file named in this way is attached to the initialization action of the
affected device type.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.