What is a check table and what is a value table in SAP?

Check table specified in the foreign key for the field. A foreign key links two tables T1 and T2 by assigning fields of table T1 to the primary key fields of table T2.

The T1 is called foreign key table (dependent table) and table T2 the check table (referenced table).

In some cases you can see when you define a domain that all the table fields or structure components referring to this domain should be checked against a certain table. This information can be stored in the domain by entering a value table.

The system proposes the value table as check table when you try to define a foreign key for the field or component. This proposal can be overridden.

Example:
Domain S_CARR_ID (data type CHAR, length 3) in the flight Model describes the three-place code of the airlines. All the airlines are listed together with their codes in table SCARR. It is generally advisable to check fields referring to domain S_CARR_ID against table SCARR. SCARR is therefore entered as value table for domain S_CARR_ID. If you want to define a foreign key for a field referring to S_CARR_ID, SCARR is proposed as the check table.

A check is not implemented by simply entering a value table! The check against the value table only takes effect when a foreign key has been defined.