Oracle sequence caching

Question

I am trying to implement a sequence in an Oracle database to act as a surrogate key creator for a table. For performance reasons, I want this sequence to be cached. I have rea

Answer 1

Turns out that this is not (or no longer true). Shut down and restart of instance does not lose cached values. Simple test with cache = 1000.

SQL> select ordered.currval from dual;

CURRVAL

    22

SQL> select unordered.currval from dual

CURRVAL

    24

SQL> SHUTDOWN IMMEDIATE SQL> STARTUP

NEXTVAL

    23

SQL> select unordered.nextval from dual;

NEXTVAL

    25

Also, ALL_SEQUENCES.LAST_NUMBER does not hold the last last number provided by the sequence except on startup and before first NEXTVAL. After first NEXTVAL, it holds last number served plus CACHE_SIZE. This does not change until new cache is generated. However, on shutdown, it apparently gets reset to just the last number served.