AW: Are there any perfomance issues associated with using a single sequence for large transaction volumes?

Hellgren, Johan wrote
> 
> Hello list,
> 
> We are currently developing a large e-commerce site using SAPDB
> 7.4.3.27. We do expect to see a large number of inserts into the
> database, and are therefore considering how to assign key values for
the
> inserted rows. Using a sequence is what we presently consider doing,
as
> it has served us well in past, smaller implementations.
> 

The implicit used primary key, called syskey CHAR (8) BYTE, which can be
selected when specifying SYSKEY in the select-list afterwards does not
serve your needs?

> I see in the documentation that sequences can be created with maximum
> values up to 38 digits, but I have been unable to find any mention of
> any issues associated with using a single sequence for very high
> transaction volumes. I'd thus like to ask the list if there are any
> recommendations for the maximum number of transactions (nextval
selects)
> per second (or other volume-based metric) a single sequence can
support
> without having locking or other performance issues. 

Why do you want to do NEXTVAL-selects? Do you use the NEXTVAL-value in
more than one row? If not, then use <sequence_name>.NEXTVAL in the
insert itself to shorten the way and avoid superfluous communication
between application/client and server.

On the other hand: when using sequences very heavily, it is a good idea
to use the CACHE-option when creating the sequence.
http://dev.mysql.com/doc/maxdb/en/6d/117c29d14811d2a97400a0c9449261/fram
eset.htm 

The cache will be good for performance, but will cause the loss of some
numbers in case of shutdown of the server.

> Also, are there any
> changes in sequence performance in MaxDB 7.5 (and 7.6) compared to
SAPDB
> 7.4?
> 

No

Elke
SAP Labs Berlin


> Thanks in advance for your insight!
> /Johan Hellgren
> 
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