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Former Member
Oct 15, 2013 at 12:09 PM

Possible I/O Performance Problem - 'direct path read'

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We are encountering intermittent performance problems in our ECC system and have found that there are occassionally ver high I/O response times. In particular, we identified high 'direct path read' for a session analysed.

A user reported a problem scrolling in transaction MIRO, so we performed a trace in ST12:

It took on average ~30 seconds to scroll one page. The above was the trace for that period.

The DB performed a FTS on RBKP:

Number of rows:

Shouldn’t be too big of a deal, right?

I identified the Oracle session and extracted the ASH data. The poor response times appear to be related to the wait event ‘direct path read’. I plotted the session against the wait event with 'Time Waited' (filtered on object RBKP):

From this (for me), there is clearly an I/O bottleneck. However, why is the optimizer choosing a ‘direct path read’ to retrieve this data? It would also be good to know how reliable the ASH stats are in relation to these events?

Thanks,

Tony

Attachments

ST12.png (30.6 kB)
FTS_RBKP.png (17.9 kB)
SE16_RBKP.png (5.3 kB)