SRLSEG is managed by using the data file host header to maintain the serial numbers used by key segments across all partitions. SRLSEG key segments can be used to make a key value unique, and this still works with partitioned files.
FairCom DB V11.0 and later supports disabling/enabling SRLSEG with a PUTIFIL() call and during compact and rebuild when the updateIFIL option is specified. A file that contains an extended header now supports turning the SRLSEG or SCHSRL segment mode on or off by:
Note: A call to rebuild or compact will fail with error IAIX_ERR (608) if the key segment definitions specified by the caller change the serial number attributes (either turning serial number on or off or changing its location in the record) when the updateIFIL option is not specified in the tfilno field of the IFIL structure.