TSOKEY00 contains TSO/VTAM time sharing parameters. Starting TSO/VTAM time sharing activates the terminal control address space (TCAS). The function of TCAS is to accept TSO/VTAM logon requests and to create an address space for each TSO/E user. TCAS builds a TCAS table (TCAST) and inserts the parameter values into it. The VTAM® terminal I/O coordinator (VTIOC), which is the interface between TSO/E and VTAM, uses these values to control the time sharing buffers, the maximum number of users, and other operational variables.
TSOKEY00 or an alternate member name may be specified by using the MEMBER operand or the keyword operand (overriding keyword MBR) of the operator START command, or by coding it into the PARMLIB DD statement of the cataloged procedure evoked by the START command. If a member name is not specified but a parmlib name is specified (on the PARMLIB DD statement), the system defaults to TSOKEY00. If neither a member name nor a parmlib name is specified, default values in the TCAS program are used.
If, during TCAS initialization, an I/O error occurs after some of the values have been read from parmlib, the default values in the TCAS program supply the remaining parameter values for the TCAS table.
If the specified value for a parameter does not fall within the value range, the default value is used.