Re: What is lock type 'KO' in v$lock table?

"Mladen Gogala" <mgogala.spam-me-not_at_verizon.net> wrote in message news:pan.2006.09.24.05.38.42.467739_at_verizon.net...

>

    No you didn't, you just didn't know they were happening.

> Why would a direct read trigger a checkpoint?

    Because there may be blocks in the buffer with commited     changes that have not been written to disc. Since a direct     path read goes to disc, bypassing the buffer, it won't see     those changes. So you have to issue a "localised" checkpoint     for the object just before the query starts to run.

    This feature existed back in (at least) 7.2 where I first met it     as the "extent checkpoint" - where I think Oracle issued a     checkpoint once per extent. At some point this turned into     a tablespace checkpoint because "extent checkpoints" were     a disaster (no checkpoint queue until 8.1). The it became the     segment checkpoint - then in 10.2 Oracle put a linked list     into the buffer header to deal with all the problems if handling     a single segment in large buffers.

-- 
Regards

Jonathan Lewis
http://www.oracle.com/technology/community/oracle_ace/ace1.html#lewis

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