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Former Member
Oct 15, 2013 at 12:09 PM

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


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?




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