SAP READ ITAB SY TABIX documentation, setup help and example usage

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Latest notes:
Note that the
sy-tabix system field is always set in relation to the used table key. If the value of sy-tabix is used as an index specification following the execution of the READ statement in another processing statement for the internal table, the same table key should be used there, whereby it is important to note that the primary index is always addressed if there is no explicit key specification.