IBM Professional Series User Manual page 295

count
is the minimum number of characters that must be
entered for the synonym to be accepted by CMS.
If
omitted, the entire synonym must be entered (see the
following example).
A table of command synonyms is built from the contents of
this file. You may have several synonym files but only one
may be active at a time. For example, if the synonym file
named MYSYN contains:
COPYFILE CPY
then, after you have issued the command:
synonym mysyn
the synonym CPY can be entered as a command name to
execute the COPYFILE command. It cannot be truncated
since no count is specified.
If
MYSYN SYNONYM
contains:
ACCESS GETDISK 3
then, the synonyms GET, GETD, GETDI, GETDIS, or
GETDISK can be entered as the command name instead of
ACCESS.
If you have an EXEC file named TDISK, you might have a
synonym entry:
TDISK TDISK 2
so that you can invoke the EXEC procedure by specifying
the truncation TD.
The Relationship between the SET ABBREV and SYNONYM
Commands: The default values of the SET and SYNONYM
commands are such that the system synonym abbreviation
table is available unless otherwise specified.
The system synonym abbreviation table for the FILEDEF
command states that FI is the minimum truncation.
Therefore, the acceptable abbreviations for FILEDEF are:
FI, FIL, FILE, FILED, FILEDE, and FILEDEF. The
7-122 VM/PC Users Guide