Re: SSD: Does a CHGPF move the data off immediately?

On 19-Jan-2012 05:06 , rob@xxxxxxxxx wrote:

Let's say you have a table with UNIT(*SSD). You also have
smsetstayoffssd set in SST. Now you do a CPYF or CRTDUPOBJ of that
table for testing reasons.

No idea about the effect of that service tool. IMO the effect of the file.mbr [dataspace] attribute should override a general SM request to avoid SSD, because the UNIT(*SSD) is an explicit request. Really depends on what the Storage Management decided to implement as the effect of their tooling... so whatever documentation they provide is the only definitive answer.

You then do a CHGPF on the new object to
change it from UNIT(*SSD) to UNIT(*ANY). Is it immediately moved off
of SSD or do you have to run:

STRASPBAL TYPE(*MP) ASP(1) TIMLMT(*NOMAX) SUBTYPE(*CALC)
or
STRASPBAL TYPE(*MP) ASP(1) TIMLMT(*NOMAX) SUBTYPE(*SSD)
afterward to get the data moved off of the SSDs?

<<SNIP>>

The movement of data is performed asynchronous to the change-request in some SM tasks. Presumably after the dataspace [or each segment] is identified with the preference, an event is signaled to request the action of those tasks which over time would reflect the change in preference.

_i Performance Value of Solid State Drives using IBM i i_
www.ibm.com/systems/resources/ssd_ibmi.pdf
"
...

When CHGPF UNIT(*SSD) or ALTER TABLE UNIT SSD is specified, DB2 will asynchronously move the file to SSD storage if available. When CHGPF UNIT(*ANY) or ALTER TABLE UNIT ANY is specified, DB2 will asynchronously move the file to traditional disks, if available. An exclusive lock is required to change the media preference, but once changed, the exclusive lock is released and the asynchronous move will continue in background tasks.

Individual partitions of an existing partitioned table can be changed to specify a media preference. The SQL statement ALTER TABLE supports a UNIT clause on a partition. For example:

ALTER TABLE sales
ALTER PARTITION sales2008
STARTING('2008-01-01') ENDING('2008-12-31') UNIT ANY
ADD PARTITION sales2009
STARTING('2009-01-01') ENDING('2009-12-31') UNIT SSD

...
"

Regards, Chuck