Tip #249 – Avoiding a System Lockup


Tip #249
Avoiding a System Lockup

With Valentine’s Day week quickly approaching, you and your staff will be very busy in the next few days.

Most of the very few calls I get during this time is from someone whose system has locked up.

System lockups are caused by locked files.  When flowerSoft writes data to an existing record in the database, it must lock that record to prevent another user from accessing the same record and destroying the integrity of the database.  As soon as this data is written, flowerSoft releases the lock on the record allowing other users to access the same record.

The record that gets locked most often is the control record.  Why?  Because this is the record that holds most of the settings and information used by flowerSoft.  For example, one of the fields in this record holds the next invoice number to be used.  So every time flowerSoft must assign an invoice number to a new order, it has to access this file and retrieve the next invoice number to be used.

In order to perform this action, flowerSoft must lock the record so that no other computer in the network will access the same record and retrieve the same next invoice number to be used as this would result in duplicate invoice numbers.

After flowerSoft retries the next invoice number to be used, it adds one to that field and then unlocks the record so that the next station needing an invoice number will retrieve the correct “next invoice number” from the record.

This is just a simple example of what record locking constitutes to give you an idea of what goes on behind the scenes.

Control record lockups are unusual because normally flowerSoft locks the record, retrieves information, writes new data and unlocks the record in a fraction of a second and there is a very small chance of another station trying to access the control record at the same exact time.

However, during extremely busy periods like Valentine’s Day week, this may become a more common occurrence.  If this occurs, flowerSoft will display at the bottom of the screen “Waiting for Control Record Number 1 to be Unlocked”.

This message should last for a very small period of time.  A couple of seconds at most.  If it lasts longer than that, someone has somehow managed to keep that record locked, preventing other users from accessing it.  This, of course, locks up the system for every one.

So how do we release the lock on the record?  By going to the offending workstation and removing the message that is on the screen.

The only way to find out which one is the offending station is by going to each one and seeing if they have an unusual message on the screen.  One you find it, either hit enter to remove the message or if the message will not go away, re-boot that computer and log back in.  Just re-booting the computer will not solve the problem, you must log the user back into the system so that the record lock is released.

Sometimes, you will not be able to find the offending workstation because the user either  shut the monitor or computer down.  If all the stations are still locked up and you cannot find the station that is causing the lockup, you must re-boot the server.

Re-booting the server will remove all the record locks, so you should be OK after it comes back up.

The best advice I can give you is to instruct your users not to leave any messages on the screen for an extended period of time.  Read the message, write it down if necessary and then hit the enter key to remove it from the screen.  This normally releases any locks the station had on other records.

So let’s keep this in mind and have a Valentine’s Day week without too much stress, especially the stress you get when your system locks up and no one can use it.

A happy and prosperous Valentine’s Day week to all of you.

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