The USERMOD sample for the System Parameter Block for the IBM CICS Interface for Teradata (HSHSPBC) is TDU0009 in dbcpfx.SAMPLIB.
HSHSPBC is used to specify the initial and maximum number of free control blocks and buffers maintained on the free chain. This also determines the number of control blocks allocated for CLI.
The allocations can be changed using the Teradata/CICS command transaction, DMEM.
For more information on using and modifying HSHSPBC, see IBM CICS Interface for Teradata Reference, B035-2448.