ACT01_UPDATE_RELEVANT is a standard SAP Structure so does not store data like a database table does. It can be used to define the fields of other actual tables or to process "Fields relevant to update from AFVC,V,V (sim. vers.)" Information within sap ABAP programs. This is done by declaring abap internal tables, work areas or database tables based on this Structure. These can then be used to store and process the required data appropriately. i.e. DATA: wa_ACT01_UPDATE_RELEVANT TYPE ACT01_UPDATE_RELEVANT.
The ACT01_UPDATE_RELEVANT table consists of various fields, each holding specific information or linking keys about Fields relevant to update from AFVC,V,V (sim. vers.) data available in SAP. These include PLNKN (Number of the task list node), PLNAL (Group Counter), PLNTY (Task List Type), VINTV (Increment between referenced operations)... See below for full list along with technical details, documentation, text table, check tables, foreign key relationships, conversion routines, relevant tcodes and example ABAP select code etc. .