Man, did I ever inherit a mess... seems that the previous unix admin needed to add more hard disks for the TSM DB2 database, so he added just one physical hard dive, created the vg's and lv's, and then gave the additional space to TSM's DB2 DB.

The issues are:
1) I now have a horrible exposure since part of the DB2 DB is not mirrored.
2) The physical space allocated for the DB2 Data Base is larger than it needs to be...

My Questions:
1) I know that I can create new VG's and LV's that are the size that I need (smaller than the current ones). plus insure that they are mirrored.
2) I know that I can copy over the physical files that DB2 has created on these LV's
3) I know that I can mount the new LV's over the LV's that TSM's DB2 is using today..

What I don't know is:
1) Since DB2 thinks it has a larger size available today, if I move the files to a smaller filesystem... will DB2 choke?

My overall goal is to get the DB2 Database, Logs, etc onto smaller filesystems, and insure that they are mirrored...

Any help would be greatly appreciated, as TSM and DB2 are new items on my plate.

DB2 does not "think" outside its boxes (files, that is). The only problem might be if DB2 uses raw devices as containers; in that case you would need something like a redirected restore to move to smaller LVs. Otherwise, as long as you create the same filesystems on your new LVs and all DB2 files fit into these filesystems, I would not expect any trouble.

If you have DB2 Health Monitor enabled and the new filesystem utilization is above the set thresholds, you will get alerts, but that's about it.