Monitor Write-Through Caching Mode - Oracle SuperCluster T5-8 Owner's Manual

Monitor Write-through Caching Mode

These topics describe maintenance relevant to Exadata Storage Servers in Oracle SuperCluster
T5-8.
"Monitor Write-through Caching Mode" on page 154
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"Shut Down or Reboot an Exadata Storage Server" on page 156
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"Drop an Exadata Storage Server" on page 158
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Related Information
See the Oracle Exadata Storage Server Software User's Guide for additional information
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about the Oracle ASM disk repair timer.
Monitor Write-through Caching Mode
The disk controller on each Exadata Storage Server periodically performs a discharge and
charge of the controller battery. During the operation, the write cache policy changes from
write-back caching to write-through caching. Write-through cache mode is slower than write-
back cache mode. However, write-back cache mode has a risk of data loss if the Exadata
Storage Server loses power or fails. For Exadata Storage Server releases earlier than release
11.2.1.3, the operation occurs every month. For Oracle Exadata Storage Server Software release
11.2.1.3 and later, the operation occurs every three months, for example, at 01:00 on the 17th
day of January, April, July and October.
1. To change the start time for when the learn cycle occurs, use a command similar
to the following. The time reverts to the default learn cycle time after the cycle
completes.
CellCLI> ALTER CELL bbuLearnCycleTime="2011-01-22T02:00:00-08:00"
To see the time for the next learn cycle, use the following command:
2.
CellCLI> LIST CELL ATTRIBUTES bbuLearnCycleTime
The Exadata Storage Server generates an informational alert about the status of the caching
mode for logical drives on the cell, for example:
HDD disk controller battery on disk contoller at adapter 0 is going into a learn cycle.
This is a normal maintenance activity that occurs quarterly and runs for approximately
1 to 12 hours. The disk controller cache might go into WriteThrough caching mode during
154 Oracle SuperCluster T5-8 Owner's Guide • May 2016