jdb_fixopen from system/extras/util/debugs.ijs will throw an exception when it tries to modify a memory mapped file.
I believe the significant lines are: t=. y t=. jdb_curtail ,t So, if you are debugging a verb where (for example) y is a large mapped file, and you get any kind of error in that verb, the file will be damaged if you have not anticipated the problem and made the file read only. One way you could anticipate the problem would be to have had the file get corrupted, and recover the file from backup and mark the file read-only before reaching the part of the code that needed debugging. This is in J6. I expect it would happen in J7, if J7 had a debugger. -- Raul ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
