Sony CDM-Z5 User Manual page 38

Delete all entries
You can delete all entries. Each entry is a space in memory for the name
and numbers . One person may have more than 3 numbers in their entry.
All entries are erased from the phone memory, including the phone
numbers, customs and all own numbers. Names and numbers in the SIM
are not erased. However, the framework of entries in the SIM is erased.
Each number remains listed individually under its name. Therefore,
names are listed repeatedly for each number that was entered under them.
GB
38