Why are there random breaks in auto-generated Help Desk Request number sequences?

At times you might notice random breaks in the auto-generated help desk request number sequence. For instance, help desk request numbers jump from 3012 directly to 4010, with no help desk request numbers between.

The help desk request sequence is maintained by the database sequence. The database sequence uses cache space to reserve the values for sequential numbers. The default size for the cache is 1000 for best performance. So the first 1000 numbers are booked for the sequence when the database starts and all new help desk requests are assigned with sequential numbering, such as 1 to 1000. When the database refresh happens, the cache is cleared and the next 1000 numbers are reserved. So, if the previous 1000 number allocation hasn't been completely used, say it stopped at number 987, after the refresh, the help desk request numbers will nonetheless begin at number 1001.