oracle里cache 20,双节点的rac，序列cache 20是否够用？

查了一下

rac用order选项时，不会cache！！！

order只对ops/rac有意义。单节点应该本身就是order的。

http://www.examda.com/oracle/zhonghe/20071018/101655394-2.html

CACHE

specifies how many values of the sequence Oracle preallocates and

keeps in memory for faster access. The minimum value for this

parameter is 2. For sequences that cycle, this value must be less

than the number of values in the cycle.

NOCACHE

specifies that values of the sequence are not preallocated.

If you omit both the CACHE parameter and the NOCACHE option, Oracle

caches 20 sequence numbers by default. However, if you are using

Oracle with the Parallel Server option in parallel mode and you

specify the ORDER option, sequence values are never cached,

regardless of whether you specify the CACHE parameter or the NOCACHE

option.

ORDER

guarantees that sequence numbers are generated in order of request.

You may want to use this option if you are using the sequence

numbers as timestamps. Guaranteeing order is usually not important

for sequences used to generate primary keys.

NOORDER

does not guarantee sequence numbers are generated in order of

request.

If you omit both the ORDER and NOORDER options, Oracle chooses

NOORDER by default. Note that the ORDER option is only necessary to

guarantee ordered generation if you are using Oracle with the

Parallel Server option in parallel mode. If you are using exclusive

mode, sequence numbers are always generated in order.