PTF, APAR, and USERMOD SYSMOD IDs

The IBM® convention for the SYSMOD ID of a service SYSMOD (APAR, APAR fix, PTF) or USERMOD is tannnnn, where:
t
identifies the type of SYSMOD. It is a single alphanumeric character. These are the values used by IBM:
A–K
Used by IBM for various levels of an APAR fix
L–T
Available for users
U
Used by IBM for PTFs
V–Z
Used by IBM for various levels of an APAR fix
a
is any alphabetic character (A-Z). Any valid character can be used for user SYSMODs.
nnnnn
is an additional identifier for the SYSMOD. For PTFs and APAR fixes supplied by IBM, it is a number from 00001 to 99999. Any valid characters can be used for user SYSMODs.