非常简单的记录，没有可读性，留作一个疑惑。

第一个节点更新数据块
第二个节点更新同样的数据块
由于是更新操作，因此需要块的current block
第二个节点像第一个节点要求current block，再发送前，第一个节点需要pin住此块，把log buffer内的内容写磁盘。
统计量里的gc current block pin time gc current block flush time分别对应了此种情况。但是我模拟的情况，发现并没有发生统计量的增加。

节点1：
test@ILSP>select
2 statistic#,
3 name,
4 value
5 from
6 v$sysstat where statistic# in (215,216);

STATISTIC# NAME VALUE
---------- ---------------------------------------------------------------- ----------
215 gc current block pin time 68
216 gc current block flush time 7019

test@ILSP> update t_one set v1='10' where n1=265 and rownum=1;

1 row updated.

test@ILSP>
test@ILSP>select
2 statistic#,
3 name,
4 value
5 from
6 v$sysstat where statistic# in (215,216);

STATISTIC# NAME VALUE
---------- ---------------------------------------------------------------- ----------
215 gc current block pin time 68
216 gc current block flush time 7019

节点2：
test@ILSP>select
2 statistic#,
3 name,
4 value
5 from
6 v$sysstat where statistic# in (215,216);

STATISTIC# NAME VALUE
---------- ---------------------------------------------------------------- ----------
215 gc current block pin time 67
216 gc current block flush time 6906

test@ILSP> update t_one set v1='10' where n1=266 and rownum=1;

1 row updated.

test@ILSP>
test@ILSP>select
2 statistic#,
3 name,
4 value
5 from
6 v$sysstat where statistic# in (215,216);

STATISTIC# NAME VALUE
---------- ---------------------------------------------------------------- ----------
215 gc current block pin time 67
216 gc current block flush time 6906

但是，另一个场景却发生了：

test@ILSP>begin
2 for i in 1 ..100000 loop
3 UPDATE wxh_tbd SET object_name=20 where rowid='AAAVaMAAEAAABDjAAA';
4 commit write immediate wait;
5 end loop;
6 end;
7 /

test@ILSP>begin
2 for i in 1 ..10000 loop
3 UPDATE wxh_tbd SET object_name=20 where rowid='AAAVaMAAEAAABDjAAB';
4 commit write immediate wait;
5 end loop;
6 end;
7 /

sys@ILSP>select
2 statistic#,
3 name,
4 value
5 from
6 v$sysstat where statistic# in (215,216);

STATISTIC# NAME VALUE
---------- ---------------------------------------------------------------- ----------
215 gc current block pin time 72
216 gc current block flush time 7502

2 rows selected.

sys@ILSP>/

STATISTIC# NAME VALUE
---------- ---------------------------------------------------------------- ----------
215 gc current block pin time 73
216 gc current block flush time 7545

2 rows selected.

sys@ILSP>/

STATISTIC# NAME VALUE
---------- ---------------------------------------------------------------- ----------
215 gc current block pin time 73
216 gc current block flush time 7570

2 rows selected.

sys@ILSP>/

STATISTIC# NAME VALUE
---------- ---------------------------------------------------------------- ----------
215 gc current block pin time 74
216 gc current block flush time 7591

我的版本是11.2.0.3，我的猜想，可能是ORACLE做了优化，再发送current block前检查下对应的日志有没有写磁盘，如果已经写磁盘了，就不需要再去做pin和flush的操作了。

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gc current block pin time gc current block flush time 疑惑

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