Unprotected screen option

IMS allows you to leave the screen in unprotected status when an output message is sent to the 3270 display and the message is formatted by MFS. This option is provided on a terminal-by-terminal basis or on a message-by-message basis, except messages bypassing MFS.

The terminal option of unprotected status applies to:

If you do not select the unprotected screen option your messages that are formatted by MFS with user-supplied formats or IMS-supplied default formats, and IMS-generated messages, leave the screen protected or unprotected on a message-by-message basis.

If the message is paged, the screen is unprotected between pages. Therefore, this option is not recommended for paged messages.

Use this option through one of the following:

Byte 1, bit 5 in the DSCA= operand of the DEV statement and in the SCA output message option of the MFLD statement is defined for protecting or not protecting the screen when the message is sent to the 3270 display:
B'0'
Protects the screen when output is sent. B'0' (protected) is the default. This bit is used for autopaged output in ISC.
B'1'
The screen is unprotected when output is sent.

If the DSCA value is set to B'0' and PROT (protected) is specified or used as the default on the TERMINAL or TYPE macro, the application program can request that the screen be unprotected when this output is sent (by setting the SCA value to B'1'). If unprotected status is requested when operator logical paging (OLP) is used for the message (PAGE=YES is specified in the corresponding MSG definition), then OLP is reset. You can modify IMS-supplied default formats to set the DSCA value to B'1'.

Whether your messages that bypass MFS leave the display protected or unprotected depends on the OPTIONS specification on the TERMINAL or TYPE macro during system definition. The default is protected.

If MFS formats an IMS message sent to the SYSMSG field of a user-defined format the screen is protected or unprotected depending on the DSCA or SCA option of the format on the device.

When the display is in unprotected status, IMS can send output to the terminal at any time. If you press ENTER, a PA key, or a PF key just before the IMS output, your input or request can be lost. This can be avoided if MFS is used for output and input and you enter the NEXTMSGP function or press PA3 (if PA3 is not used for copy) to obtain protected status before entering input data.

If MFS is not used or is only used for output, and the MOD name specifies DFS.EDT, then PA3 protects input data and must not be used for copying.

The following table illustrates the action to be taken (protected or unprotected) by IMS based on the OPTIONS specification on the TERMINAL or TYPE macro during system definition, and the type of output message sent.

Table 1. IMS protect or unprotect action based on OPTIONS specification
Output Message IMS System Definition (PRO) IMS System Definition (UNPRO)
IMS-generated message with: DSCA|SCA=PROTECT PROTECT UNPROTECT
IMS-generated message with: DSCA|SCA=UNPROTECT UNPROTECT UNPROTECT
Message using MFS bypass PROTECT UNPROTECT
Your message using MFS and user-supplied format or IMS-supplied default format with: DSCA|SCA=PROTECT PROTECT UNPROTECT
Your message using MFS and user-supplied format or IMS-supplied default format with: DSCA|SCA=UNPROTECT UNPROTECT UNPROTECT
Note:
  1. PROTECT: Do not send additional output; wait for input.
  2. UNPROTECT: Send output if an output message is available and eligible to be sent.