Oracle 23c New Features for DBA'sIn 18c, the sequences can be scalable. Means the sequences will have an append of extra numbers with following formula.
scalable sequence number = 6 digit scalable sequence offset number || normal sequence number
6 digit scalable sequence offset number = 3 digit instance offset number || 3 digit session offset number.
The 3 digit instance offset number is generated as [(instance id % 100) + 100]. The 3 digit session offset number is generated as [session id % 1000].
This will help to relieve the index contention and sequence cache problems in RAC since the value has large difference in values, this sequences are useful in typical loads where non primary /unique based key constraint data is not there.
As you see the ID column value of next val is showing as 101274001, instead of 1. So if we interpret the above formula
Instance 1 = 1/100 - 100.1 --> round to 101.
SID = 274
00 = Prefix to scale the sequence with three digits
1 - Original sequence number
101||274||001
You can also have extend, no extend option with scale when you create scalable sequences.
-Suresh
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