FS6200 Server System Implementation Guide - Public Support ...

I/O Time
• ACQUIRE
• FREE
• OL
• RF
• SC
• UR
Refer to the System Commands Reference Manual for further details on the preceding
commands.
The FS6200 Server I/O architecture is capable of having multiple I/Os active to a disk at a
time, resulting in improved throughput and I/O rates on FS6200 Server systems, especially
when doing a heavy I/O load to VSS2 disks. However, this can cause I/O time reported on
the FS6200 Server to be larger than on previous MCP systems because it is accumulated
simultaneously for these multiple active I/Os. Larger I/O time is simply an accounting
difference that occurs because some of the I/O queue is in the storage system on the
FS6200 Server.
Larger I/O time does not mean it takes longer to perform I/O operations. On the contrary,
reductions might occur, potentially resulting in smaller elapsed times for program
execution than on other MCP systems of the same performance level.
As a result, you cannot meaningfully compare I/O time on the FS6200 Server to I/O time
on previous MCP systems. Larger I/O time is expected (up to 8 times larger) and does not
indicate a problem. What matters are statistics like overall I/O rates and the elapsed time
of transactions. These increased I/O times can be seen in the ACCUMIOTIME task
attribute as well as I/O times recorded in file close and end-of-task SUMLOG records.
If you use the IOTIME queue attribute or the MAXIOTIME task attribute, you might need
to increase the values you assign to these attributes.
Performing Dynamic PCD Updates
The I/O configuration of the MCP is more flexible on the FS6200 Server than on previous
MCP systems. You can place new devices, not yet in the PCD, into use by the MCP
without performing a halt/load operation.
Perform the following steps to dynamically place devices into use:
Operating the Server
Note: This procedure should not be done while the MCP is executing a heavy I/O
workload as some steps take longer and could possibly time out.
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