3GPP TSG-T3 (USIM) #3	Tdoc T3-99070
16-18 th of March, 1999
Espoo, Finland

Alignment of number of records in a linear data field with ISO/IEC 7816-4

Source :Nokia

GSM 11.11 allows the maximum number of records in a linear data field to be 255, record number '0' is not allowed. ISO/IEC 7816-4 specifies the maximum number of records in a linear data field to 254 where record number '0' and 'FF' is not allowed. 

When introducing the concept of index files the usage of 'FF' as a record number becomes important. The administration file in the index file concept contains pointers to records in other files. As 'FF' indicates a valid record number the administration file records must be personalised to '00' with respect to the content of the record pointers. It means that in order to allow 255 records personalisation of the administration is necessary. The value '00' as a record pointer indicates that there is no entry in the data field associated with the pointer. 

Personalisation values other than 'FF' must be written to the data field. Writing data to an EEPROM memory is time consuming in particular if the data field is large.

There is no backward compatibility issue related to this as data fields that contains 255 records can be identified from the status information. Currently there is only the ADN field that may have this constraint. It is only a question of not personalising data fields to contain more than 254 records.

From the USIM implementation point of view it would be a benefit to align the specification with ISO/IEC 7816-4.