Possible uses

Some possible uses of the PRINTDS exits are described below:

Restrict certain users from using the PRINTDS command
The initialization exit can check the user ID and decide, based on your own criteria, to cancel the PRINTDS command. The exit can first display an informational message to the user, for example, using PUTLINE. The exit can then set a return code of 16 and return to the PRINTDS command processor.
Change the operands that have a fixed default value
The PRINTDS initialization exit receives the default exit parameter list (DEPL). The DEPL contains the default values of PRINTDS operands that have a fixed default value. The exit updates the appropriate values in the DEPL, sets a return code of 0, and returns to the PRINTDS command processor.
Change the operands that the user specifies on the command
You can use the initialization exit to change the operands that users specify on the PRINTDS command. The initialization exit receives the DEPL, which it can use to change the fixed default values of specific operands.
The initialization exit also receives the address of the command buffer. It can change the operands the user specifies on the PRINTDS command by using a new command buffer. For example, the initialization exit can scan the command buffer to:
- Look for conflicts with the operands a user specifies and correct any errors. For example, the user cannot specify both the TITLE and CCHAR operands on the PRINTDS command.
- Prevent users from specifying certain operands or certain values for operands.
To check the command buffer and change its contents, the initialization exit can:
- Scan the command buffer and decide, based on your own criteria, to change the command the user issued
- Obtain storage for a new command buffer
- Build the new command buffer
- Update the key, length, and data fields for the new command buffer as follows:
  Key
  
  X'02'
  
  Length
  
  the length of the new command buffer
  
  Data
  
  the address of the new command buffer
- Set a return code of 0 and return control to the PRINTDS command processor.
The exit must not change the command buffer it receives. It must create a new command buffer and return the address of the new command buffer to PRINTDS. For more information about the command buffer and the new command buffer, see TSO/E standard exit parameter list. For information about the format of the command buffer, see Command buffer.

You must also write a termination exit to free the storage the initialization exit obtains for the new command buffer. When the PRINTDS command processor invokes the termination exit, it passes the address of the new command buffer to the termination exit. The termination exit frees the storage for the new command buffer.
Provide installation-defined pseudo-operands
If users at your installation print data sets with the same types of characteristics, you can define pseudo-operands that are equivalent to two or more PRINTDS operands. Providing pseudo-operands makes it easier for users to issue the PRINTDS command. Users need not remember several PRINTDS operands. They can specify the pseudo-operand.
For example, you could associate a pseudo-operand named PRTINV with three PRINTDS operands. The initialization exit can scan the command buffer. If the exit finds the pseudo-operand PRTINV, it can:
- Obtain storage for a new command buffer
- Build a new command buffer and replace the pseudo-operand with the appropriate PRINTDS operands in the new command buffer
- Update the "Key", "Length", and "Data" fields for the new command buffer as follows:
  Key
  
  X'02'
  
  Length
  
  the length of the new command buffer
  
  Data
  
  the address of the new command buffer
- Set a return code of 0 and return control to the PRINTDS command processor.
You must also provide a termination exit. The termination exit must free the storage that the initialization exit obtained for the new command buffer.
Monitor how long it takes the PRINTDS command to complete processing.
You can use the initialization and termination exits to monitor the approximate time it takes the PRINTDS command processor to complete processing. When the initialization exit receives control, it can:
- Invoke the TIME macro
- Use the exit-to-exit communication word to return the time to the PRINTDS command processor. The exit updates the "Key", "Length", and "Data" fields for the exit-to-exit communication word as follows:
  Key
  
  X'01'
  
  Length
  
  the length of the data (time)
  
  Data
  
  the data (time)
- Set a return code of 0 and return to the PRINTDS command processor.
When the termination exit gets control, it receives the time from the initialization exit in the exit-to-exit communication word. Before the termination exit returns control to PRINTDS, it can invoke the TIME macro. The exit can calculate the time difference between the time from the initialization exit (in the exit-to-exit communication word) and the time it receives from issuing the TIME macro. The result is the approximate time it took the PRINTDS command to complete its processing. The termination exit can include the processing time in a data set. You can then periodically print the data set and review the time calculations.