Before you can invoke the call attachment facility (CAF),
you must first make DSNALI available.
About this task
Part of CAF is a Db2 load
module, DSNALI, which is also known as the CAF language interface.
DSNALI has the alias names DSNHLI2 and DSNWLI2. The module has five
entry points: DSNALI, DSNHLI, DSNHLI2, DSNWLI, and DSNWLI2. These
entry points serve the following functions:
- Entry point DSNALI handles explicit Db2 connection
service requests.
- DSNHLI and DSNHLI2 handle SQL calls. Use DSNHLI if your application
program link-edits DSNALI. Use DSNHLI2 if your application program
loads DSNALI.
- DSNWLI and DSNWLI2 handle IFI calls. Use DSNWLI if your application
program link-edits DSNALI. Use DSNWLI2 if your application program
loads DSNALI.
Procedure
To make DSNALI available:
- Decide which of the following methods you want to use to
make DSNALI available:
- Explicitly issuing LOAD requests when your program runs.
By
explicitly loading the DSNALI module, you beneficially isolate the
maintenance of your application from future IBM® maintenance to the language interface. If
the language interface changes, the change will probably not affect
your load module.
- Including the DSNALI module in your load module when you link-edit
your program.
If you do not need explicit calls to DSNALI for CAF
functions, link-editing DSNALI into your load module has some advantages.
When you include DSNALI during the link-edit, you do not need to code
a dummy DSNHLI entry point in your program or specify the precompiler
option ATTACH. Module DSNALI contains an entry point for DSNHLI, which
is identical to DSNHLI2, and an entry point DSNWLI, which is identical
to DSNWLI2.
A disadvantage to link-editing DSNALI into your
load module is that any IBM maintenance
to DSNALI requires a new link-edit of your load module.
Alternatively, if using explicit
connections via CALL DSNALI, you can link-edit your program with DSNULI,
the Universal Language Interface.
- Depending on the method that you chose in step 1, perform
one of the following actions:
- If you want to explicitly issue LOAD requests when your program
runs:
In your program, issue z/OS® LOAD
service requests for entry points DSNALI and DSNHLI2. If you use IFI
services, you must also load DSNWLI2. The entry point addresses that
LOAD returns are saved for later use with the CALL macro. Indicate
to
Db2 which entry point to
use in one of the following two ways:
- Specify the precompiler option ATTACH(CAF).
This option
causes
Db2 to generate calls
that specify entry point DSNHLI2.
Restriction: You cannot
use this option if your application is written in Fortran.
- Code a dummy entry point named DSNHLI within your load module.
If you do not specify the precompiler option ATTACH, the Db2 precompiler generates calls
to entry point DSNHLI for each SQL request. The precompiler does not
know about and is independent of the different Db2 attachment facilities. When the calls generated
by the Db2 precompiler pass
control to DSNHLI, your code that corresponds to the dummy entry point
must preserve the option list that was passed in R1 and specify the
same option list when it calls DSNHLI2.
- If you want to include the DSNALI module in your load module
when you link-edit your program:
Include DSNALI in your load
module during a link-edit step. The module must be in a load module
library, which is included either in the SYSLIB concatenation or another
INCLUDE library that is defined in the linkage editor JCL. Because
all language interface modules contain an entry point declaration
for DSNHLI, the linkage editor JCL must contain an INCLUDE linkage
editor control statement for DSNALI; for example, INCLUDE SYSLIB(DSNALI). By coding these
options, you avoid inadvertently picking up the wrong language interface
module.