Generation of check tables; Assignment of numbers

What causes this issue?

During the generation of a data structure, check tables are created for
newly defined characteristics. A check table contains the allowed
values for a characteristic. During data entry, data records and their
characteristic values are checked against the appropriate check tables.
In the current data structure, new check tables need to be created for
certain characteristics. The name of the check table is created using a
prefix 'Txx' (e.g. 'T27' or 'T25') and a two digit number ('nn'). This
number can be assigned
manually or automatically.
In both cases, the system checks whether the name 'Txxnn' is still
available.

How to fix this error?

Decide whether you want to number the check tables manually or have
them numbered by the system automatically. If your entire R/3
configuration is contained in a single system, you can choose the
automatic assignment. If you use several R/3 systems, you should choose
manual assignment.
Note the following general points for assignment:
The check tables are created independent of client with the name
'Txxnn' in the ABAP/4 dictionary and on the database, i.e. they are
valid thoughout the system. If several R/3 systems are being customized
in parallel, e.g. test and productive system, you must make sure that
the check table numbers are also system-independent or else you will
not be able to combine the data via a transport in future as the names
will not be unique.

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Example: In a test system, you create check table 'T2724' for
characteristic M2. In the productive system which, until this point was
identical to the test system, you also create a check table 'T2724'
(with another description) as number 24 is still available, however,
you assign characteristic M3 to this table. From now on, you can no
longer transport from the test system into the productive system.
SAP recommendation:
Assign the check table numbers manually and make sure that the same
numbers are not assigned in different systems.
You can ensure this by:
Assigning individual ranges of 10 to the test and productive systems
in order to prevent problems in transports (e.g. test system: low
numbers; productive system: high numbers).
Assigning authorizations to ensure that it is only possible to generate
in the test system and that the productive system is maintained by
transports from the test system.

Error message extract from SAP system. Copyright SAP SE.