Session Manager MISER ERB UNDERISZSMGR shifts application data right on 3270 screen

When a session is managed by ISM (UNDERISZSMGR), then the MISER setting will be used. In this instance, MISER=ERB was set to emulate a read buffer command. Setting MISER=OFF or NO solved the problem where the updated application screen was no longer shifted to the right.

The IBM Session Manager Installation and Customization manual GC34-2804-00 in Chapter 12 on page 329 in topic 'Incompatibilities between MISER and non-miser operation'

Incompatibility may occur when emulating the RBUF command. This command is used when MISER ERB has been specified to request Read Buffer emulation. The command returns the entire terminal buffer, including nulls. The RMOD command does not return nulls, and since this is used in RBUF emulation, incompatibility exists.

This might be noticed where a terminal user has positioned the cursor away from the beginning of a field, by use of the cursor movement keys rather than the space bar, and entered data. The gap between the beginning of the field and the data may be filled with nulls. If the application performs an RBUF to the terminal, the nulls will be in the inbound data stream and the application can determine where the data was entered on the screen. With MISER RBUF emulation, it appears to the application that the data has been entered at the beginning of the field. Should the screen be redisplayed, the data in the field will appear to have moved to the left.

If this incompatibility is considered to outweigh the benefits of network data traffic reduction, then RBUF emulation may be selectively disabled by specifying the MISER options for the particular application as:

MISER INPUT OUTPUT

omitting the ERB option which requests RBUF emulation.