M*******y
发帖数: 14 | 1 Hi there,
I am performing a very simple experiment with DB2.
The query is: select count(*) from table1
I am interested in the disk I/O activities.
Is there any way to ensure disk access? I.E. to clear
the database's cache. The 2nd (and later)run is lightening fast, presumably no
disk access.
I've tried
1. db2stop, clear the OS cache, db2start
2. select * from some large junk tables and then repeat 1.
The query still runs very fast.
Thank you in advance.
cha | f*******h
发帖数: 1269 | 2 DB2 keeps statistical information of tables, such as the total count of
tuples. Thus your count query is always superfast. You have to try something
else.
no
【在 M*******y 的大作中提到】
: Hi there,
: I am performing a very simple experiment with DB2.
: The query is: select count(*) from table1
: I am interested in the disk I/O activities.
: Is there any way to ensure disk access? I.E. to clear
: the database's cache. The 2nd (and later)run is lightening fast, presumably no
: disk access.
: I've tried
: 1. db2stop, clear the OS cache, db2start
: 2. select * from some large junk tables and then repeat 1.
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