table change and multiuser problem

[Greg Suhok]

I have been trying to implement multiuser error handling for several scripts that I have written. However, when any of them attempt to execute the change_begin() function when the record is locked by another session or user, the script will "hang" and a5 will freeze. Apparently, the error is not thrown. The script will continue to hang until the record is unlocked. Then it will finish executing normally. Here is a small test script I wrote to confirm the problem I have encountered in my other scripts,

option strict
option nobreak

dim orders as p

orders = table.open("orders.dbf")
orders.fetch_first()

on error goto RECORD_LOCKED
orders.change_begin()
on error goto 0
orders.repid = "01"
orders.change_end(.T.)

orders.close()

end

RECORD_LOCKED:
on error goto 0
ui_msg_box("Box", "Record locked by another user.")
end

Now, if I purposely attempt to modify the first record in the orders table in another session and execute this script, the script will hang when it attempts to execute
"orders.change_begin()". Any ideas on why this is happening?

[JerryBrightbill]

RE: table change and multiuser problem

Greg

When a record is open in change or enter mode, it is locked to all other users. Alpha, like most databases, locks on the record level, that is, it locks one specific record only. As long as that record is in change mode, no other user can make a change. As soon as the record is saved, then another user can edit. Other users can view the record, but can't edit.

Some scripts may open a table in exclusive mode. In that case, the whole table is locked. Normally you wouldn't want to do this, although some processes, like packing require exclusive access.

This normally isn't a big issue even in large networks as it is not normal for more that one user to be editing the same record.

Jerry

[JohnZaleski]

RE: table change and multiuser problem

Your program probably is working, you are just not waiting long enough for the results. Wait at least one minute.

Try this for faster results:

option strict
option nobreak
dim orders as p

orders = table.open("orders")
orders.fetch_first()
if orders.is_record_locked() then
goto record_locked
end if

orders.change_begin()
orders.change_end(.T.)

orders.close()
end

RECORD_LOCKED:
on error goto 0
ui_msg_box("Box", "Record locked by another user.")
end

[Greg Suhok]

RE: table change and multiuser problem

Thank you for your solutions. I was not aware that the
is_record_locked() function existed. I have tested it with my scripts and it works great.