v User packages — User-written external functions that are available to an
individual. These functions are searched before other types of function packages
and are often written to replace the other types of function packages.
v Local packages — Application or system support functions that are generally
available to a specific group of users. Local packages are searched after user
packages.
v System packages — Functions written for system-wide use, such as the TSO/E
external functions. System packages are searched after user and local packages.
Function packages written by a user or an installation must be pre-loaded at logon
time. The default name for the user packages is IRXFUSER, and the default name
for the local package is IRXFLOC. Other function packages can be named in a
parameter block set up by a system programmer.
For more information about function packages, see z/OS TSO/E REXX Reference.
Search Order for Functions
When the language processor encounters a function call, if defaults have not been
changed, it goes through the following search order:
v Internal functions — Labels in the exec that issued the function call are searched
first (unless the label is in quotation marks in the function call).
v Built-in functions — The built-in functions are next in the search order.
v Function packages — User, local, and system function packages, in that order,
are searched.
v Load libraries — Functions stored in a load library are next in the search order.
v External function — An external function and its caller must either be members in
the same PDS or members of PDSs allocated to a system library, such as
SYSEXEC or SYSPROC.
Function Packages
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z/OS V1R1.0 TSO/E REXX User’s Guide
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