SDSX.SYS in RT-11

Has anyone been able to successfully use SDSX.SYS under a Mapped RT-11 Monitor? Or does it have a bug and if so, does anyone have a fix? For as long as I can remember, I have used SDX.SYS (= SDHX.SYS) to debug my programs under RT-11. Unfortunately, the SDHX.SYS variant freezes everything in RT-11 (all jobs, device drivers, monitor and even the clock) when the program is stopped at a breakpoint. Note that DEC supplies two variants of SDX.SYS which execute under Mapped RT-11 Monitors: (a) SDHX.SYS which is called HARD (b) SDSX.SYS which is called SOFT In both cases, the file of the chosen variant MUST be copied to SDX.SYS before that variant can be used. Obviously, only one variant can be used at a time. Very recently, I had the occasion to link VDT.OBJ (the ODT variant modified into VDT) into my program and I found that other jobs were no longer frozen. I hoped that SDSX.SYS => SDX.SYS might produce the same result. However, not only does SDSX.SYS not perform in that manner, but as soon as I attempt to activate other jobs (almost always, those other jobs are KED variants executing as system jobs which display the listing for the potion of the program which is being debugged) which are in an IOWAIT state (holding for keyboard input), RT-11 usually crashes immediately, especially when the breakpoint is in the RT-11 monitor. Does anyone have any experience with SDSX.SYS which is different, specifically when SDSX.SYS actually works and still allows other jobs to execute at the same time while one job is stopped at a breakpoint under SDSX.SYS and the other jobs are KED variants which are displaying a listing of the program which is being debugged. While SDHX.SYS works perfectly, since it freezes everything when the program is stopped at a breakpoint, I had hoped that SDSX.SYS would allow the other jobs to move to other portions of the listing as other portions of the code were being executed, often instruction by instruction. In case this information is helpful, the other system jobs which are executing KED variants have opened the listing file in READ ONLY / INSPECT mode, and no other file requests are being executed. I had somehow hoped that if VDT could execute correctly but still allow other jobs to continue, that SDSX.SYS might also allow that as well. Can anyone help or at least comment? Am I doing anything wrong? Is there a bug in SDSX.SYS which no one else has found? While I am using a Mapped Monitor which has Multi-Terminal support, the same problem is present when the DEC distributed monitor, RT11XM.SYS without Multi-Terminal support is used. While <CTRL/X> must be used with the same terminal to re-activate a system job, when SDSX.SYS is used, the same problem occurs. So does SDSX.SYS have a bug and if so, does anyone have a fix? Jerome Fine