rdisp/ses_tab_max_no is a SAP Parameter attribute which is used to control 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 .
VMC-specific data is stored in VMC sessions. This parameter configures
the maximum number of VMC sessions. A VMC session can be created for
every logon by default.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.