Online alter transaction does not get terminated gracefully when cancelled - Known Error

Online alter transaction does not get terminated gracefully when cancelled Description When an alter table transaction is triggered from the UI, for example from the Dictionary, and later gets cancelled by the user or a transaction quota rule, all the corresponding triggers and temporary tables are not cleaned from the DB.

The behavior is different when adding a new field to a table, in that case the transaction is not cancellable or does not get cancelled by the quota rule, so the issue does not occur.

Steps to Reproduce

1. Open a fairly large table (>1GB) in the dictionary. 2. Alter a filed in the table by increasing the column length. 3. Wait for the transaction to get cancelled or manually cancel it using 'cancel_my_transaction.do'.

After cancelling the transaction, the 'glide.db.online_alter' threads die off, but the triggers and table are left behind.

Workaround As a result of this PRB, Database triggers and a temporary Database table are left within the instance Database.

These can not be dropped at this time via the UI, and hence it will be necessary to raise a case to ServiceNow Support to request that both the Database triggers, and the temporary Database table are dropped. ServiceNow Support will then check to ensure it is safe to perform this action on the Database, and proceed to do so only if they have confirmed the actions are necessary.