Upon initial invocation of IKJEFLN1, this parameter contains either the value from the previous T1O/E session or the value specified on the LOGON command. Upon subsequent entry to IKJEFLN1, this parameter contains the region size entered on the logon panel. You can supply a different region size to the logon panel using this parameter.

The region size is the number of kilobytes of main storage available for the TSO/E session. The maximum length of the field is 7 bytes. The maximum allowable region size is 2096128. The data contained in this parameter is in EBCDIC form.