Database Reference
In-Depth Information
Figure 7-1.
Optimal redo log configuration
You would place redo log group 1 with members A and B onto disks 1 and 3. You would place redo log group 2
with members C and D onto disks 2 and 4. If you have groups 3, 4, and so on, they'd go onto the odd and even groups
of disks respectively. The effect of this is that
LGWR
, when the database is currently using group 1, will write to disks 1
and 3 simultaneously. When this group fills up,
LGWR
will move to disks 2 and 4. When they fill up,
LGWR
will go back
to disks 1 and 3. Meanwhile,
ARCn
will be processing the full online redo logs and writing them to disks 5 and 6, the
big disks. The net effect is neither
ARCn
nor
LGWR
is ever reading a disk being written to, or writing to a disk being read
from, so there is no contention (see Figure
7-2
).
Figure 7-2.
Redo log flow
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