STVARVC

T-code STVARVC can be used for the Client independent variables (Client ‘000’).
The system variants (variant name starting with SAP& or CUS&) are cross-client and they are stored in client 000.
Therefore these variants can use TVARVC variables from client 000.
These variables can be maintained from transaction code STVARVC (see SAP Note 770084).

STVARV

T-code STVARV can be used for the Client dependent variables.
Normal report variants (which are not system variants) are client specific and they are stored in the given client.
Therefore these variants can use TVARVC variables from the specific client.
These variables can be maintained from transaction code STVARV (see SAP Note 557314).

Create and maintain parameter values in TVARVC using STVAR SAP transaction

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'.