If users do not receive the alerts that they "expect," the reason could be that data have changed again before the alerts are sent or that the batch processing system has been stopped to avoid an overload of alerts being sent to users.
Data changes before alert is generated
If a user does not receive an "expected" alert, it could be because data changed again before the event was processed, but after the event was processed, the conditions no longer matched the alert rule, so no alert was sent.
When a batch is executed, it processes the logged events and matches actual data in the database with the rule conditions. However if the data changes after the event was logged, the result could be that certain conditions are no longer met and no alerts are generated. For more information, see "Examine the risks of low batch frequency" under "Process batches for change-based events" in About alert batch execution.
Alert rules are disregarded during data import
During data import, the processing of alerts can be turned off to avoid large numbers of alerts being sent to users who have created alert rules. When the alert generation is turned off, no alerts are triggered by the data which is imported, even though some of the existing rules match conditions of the imported data. For more information, see "Turn off alert generation during data import" in About alert batch execution.
Alerts are delayed
If batch processing is set to be executed with a low frequency, alerts based on rules with a narrow time limit might not be sent in time to be of any use.
If you have specified that you want to be alerted when a purchase order is due in 2 days. If the batch is only run every second day, the purchase order might actually be due one day after you get your alert and you do not get the two-day notice that you expected.
The same is true for due-date alerts that should alert you about past due dates. For example, perhaps you might want to be alerted 5 days after a purchase order was due. If batches are only run every second day, your purchase order was actually due 6 days ago and not 5 days ago when you receive your alert. For more information, see "Process batches for due date events" in About alert batch execution.
Alert rules become obsolete and no alerts are sent
The due date alert rules can be set up with a certain amount of flexibility with regards to time limits. That is, the due date alert rules can have a built-in time allowance to allow for situations where batches are not run for a period of time. However, if the time allowance set up for alert rules is exceeded, alerts become obsolete and no alerts are sent. For more information, see "Set flexible due dates" under "Process batches for due date events" in About alert batch execution.
Event queue is deleted
If the event queue is deleted before a batch job is executed, users who have active alert rules in the system do not receive alerts that would otherwise have been generated and sent to them. For more information, see "Delete the event queue" in About alert batch execution.
Security settings have changed
If security settings changes and a user no longer has permission to access the data that forms the basis of an alert rule, no alerts generated by this rule is delivered to the user.