Use of the LIMIT parameter in Exadata IORM plan artificially throttles LGWR I/O
Last updated on FEBRUARY 06, 2014
Applies to:Oracle Exadata Storage Server Software - Version 188.8.131.52.1 to 184.108.40.206.1 [Release 11.2]
Information in this document applies to any platform.
Incorrect over-throttling of LGWR I/O operations can be seen in Exadata with image version before 220.127.116.11.0, when IORM plan is in use and with the LIMIT parameter explicitly specified.
This is an example of such IORM plan:
CellCLI> alter iormplan
dbplan=((name=ORCL1, level=1, allocation=40, limit=40, flashcache=on), -
(name=ORCL2, level=1, allocation=40, limit=40, flashcache=on), -
(name=ORCL3, level=1, allocation=15, flashcache=off), -
(name=other, level=1, allocation=5, flashcache=off))
The issue may be observed after implementing or modifying an IORM plan in Exadata.
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