Re: Synchronous writes & TEMP

How are you testing that the writes are synchronous ?

I've only checked this fairly recently so I can't make any comment about older versions of Oracle, but my observations suggest that direct writes take place without waiting for file-system sync - except for a small number, which are (I guess) the last writes in a direct write pass that your session expects to do.

I base this comment on observations of waits for direct writes using event 10046 level 8. In a simple test case, an order by on some 32 MB of data, the trace file showed only two waits for direct writes for a total of 13 blocks, even though the total volume written was clearly far in excess of 13 blocks.

There may be variations dependent on o/s, and optional extras installed at either layer.

For writes that go through the buffer I guess it's either a question of minimising code changes - or simple oversight, and someone will get around to it eventually. Unless there's some strange circumstances where Oracle might do a buffered write, followed by a direct read - and therefore manage to read an older version of the block than existed in the file-system buffer. (Seems unlikely, though)

-- 
Regards

Jonathan Lewis

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"VC" <boston103_at_hotmail.com> wrote in message
news:MqIoc.39444$xw3.2544076_at_attbi_s04...


> Does anybody know why Oracle uses synchronous writes while writing to the

> temporary tablespace ?  Presumably we do not care about data loss in this

> case.

>

> Your thouhts are much appreciated.

>

> VC

>

>

>

>