Copy documents from archive storage to cache storage.

[pankaj.puranik]

Hi

I was thinking of this situation :-

I have documents in cache storage. These documents have reached their 'n' days in cache and are now eligible for migration. I run the ARSMAINT and the documents are moved to archive storage.
                                                or
My system is set up to load files in cache as well as archive storage simultaneously.

Now the cache storage/file system gets corrupted. How can I copy the data from the archive storage back to the cache storage?


Thanks
Pankaj.

[Justin Derrick]

In most situations, you just suffer through it until the cache starts to be populated with new data -- each day that you load new files, your system gets a little faster as more and more information is loaded into the cache filesystem.

It is possible to retrieve documents from TSM, and then place them back into the cache.  I've written a utility to do this for customers to resolve performance problems created by poor caching -- situations where administrators who selected 90 days for caching, but users were accessing documents for 450 days.  arsadmin can perform this task, but I've found that it doesn't preserve expiration dates in the cache, so it creates a bigger mess than it really solves.

-JD.

[sandeepveldi]

Assuming that you still have the index intact in DB2, you should be able to do this using arsadmin -m option. CMOD will take care of creating the softlink entries under cache1 filesystem

[Justin Derrick]

Hi Sandeep.

I don't think I've ever seen arsmaint -m (cache migration) re-populate a cache filesystem.  Can you point to the documentation or technote that describes this behaviour?  I'd be interested in testing that out.

-JD.

[sandeepveldi]

It's actually "arsadmin -m" not "arsmaint -m". You can refer to the arsadmin parameters in the following web reference:
http://publib.boulder.ibm.com/infocenter/cmod/v8r4m1/index.jsp?topic=/com.ibm.ondemand.administeringzos.doc/dodad002.htm

We used it earlier to copy data from cache to TSM when we lost it in TSM. The copy is done at an object level. The arsdmin retrieve & store must be used at object level. The object names can be obtained from data tables.

Let me know in case you have any further questions.

Sandeep Veldi

[pankaj.puranik]

Sandeep,

Copying data from cache to archive storage is fine.
But here we are looking for a possibility of copying from archive storage back to cache.

Looking at the documentation, I am not getting a clear picture.
Could you explain this with an example? That could be of great help.

Here's the scenario.
I have data in archive storage only and the data has expired in cache.
Assume that I have the indexes in the DB and they are not migrated.
Now I want to copy the data back to cache from the archive storage.

What would be the steps involved?

Thanks
Pankaj.

[Justin Derrick]

Sandeep...

I've looked at the -m parameter, and it must be used in conjunction with the store or retrieve commands -- it doesn't repopulate the cache from secondary storage by itself, which is what Pankaj is looking for.

I haven't tested the latest versions of CMOD, but the problem with this method (again, in the past) has been that it places older documents back into the cache with expiration dates that don't take into consideration the age of the document -- you end up with a 'bulge' of documents that sit in the cache for weeks, months, or even years past their proper expiration date.  This makes your cache filesystem larger than it needs to be, and robs your other App Groups of storage that could be put to better use.

-JD.