A database table defined in ABAP Dictionary whose database instance is assigned to more than one table defined in ABAP Dictionary. Multiple cluster tables are grouped in a table cluster in the database. The intersection of the key fields of the cluster tables forms the primary key of the table cluster. The other columns of the cluster tables are stored in compressed form in a single column VARDATA of the table cluster. You can access cluster tables using Open SQL only. Certain other restrictions also apply.