TAPEINI is a flag to inform SCHED that the next group of input parameters will be tape initialization information, equivalent to one line from the TAPEFILE. See Section 3.4 for content details. Once the tape initialization parameters have been read, SCHED will return to reading the inputs for the current scan, usually the first.
Note that a tape initialization file is almost certainly NOT needed. Most parameters in it relate to initial tape head and pass positions which no longer make sense in the disk era. The one possibly useful parameter is the media specification, but that should be defined in the station catalog and would only be used during periods of transition.