Explanation: EXTENDEDTTOC(Y|N) is an optional parameter specifying whether DFSMShsm should use extended tape table of contents (TTOCs) in order to better utilize tapes with higher capacity volumes in your installation. Extended TTOCs allow DFSMShsm to write slightly more than one million data sets (potentially) to a migration tape or backup tape.
To use extended TTOCs in your installation, you must define your offline control data set(OCDS) with a maximum record size of 6144 bytes, as described in z/OS DFSMShsm Implementation and Customization Guide. Then enable the support by entering the SETSYS command with optional parameter EXTENDEDTTOC(Y) or its shortened form, EXTTC(Y).
To return to using non-extended TTOCs, enter the SETSYS command with EXTENDEDTTOC(N) or its shortened form, EXTTC(N).
SMS relationship: Parameter has the same meaning when applied to SMS-managed or non-SMS-managed volumes or data sets.
SETSYS default: None.
DFSMShsm default: If you do not specify this parameter on any SETSYS command, the DFSMShsm default is not to use extended TTOCs.