The CLUSTER table attribute is used in the BW Feature Package for SAP BI systems. Only use it for tables in a BW environment.
With this attribute, you configure that system no longer distributes the table contents evenly across all volumes in individual blocks of eight kilobyte pages. If possible, the system stores the table contents in larger connected blocks in the volumes instead.
SAP Note 1040431
SQL Reference Manual, System Tables FILES, MONITOR_PAGES, TABLESTORAGEDETAILS, INDEXSTORAGEDETAILS