The functionality covered by transaction STVARV and table TVARVC allows you to create single customizable parameters or select-option. So instead of creating a new ztable just to store one value you can create a parameter within here which gets stored in SAP table TVARVC and is and maintained via transaction STVARV.

Step 1 - Execute transaction STVARV
Execute tcode STVARV and you should see a list of already created parameter and selection values. In-order to create a new one click on the change icon.


Now press the create button



Step 2 - Create parameter Enter name of your parameter and press save.



Step 3 - Read parameter value
In-order to read the parameter or select-options value simply use an ABAP select statement to retrieve it from the table

select single *
  into wa_tvarvc
  from tvarvc
 where NAME eq 'ZBUFFER'.