Why are there random breaks in auto-generated SR number sequences?

At times you might notice random breaks in the auto-generated SR number sequence. For instance, SR numbers has jumped from 3012 directly to 4010, with no SR numbers between.

The SR 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 SRs 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 SR numbers will nonetheless begin at number 1001.