ALTER DBSPACE question when unloading/reloading

[Former Member]

Hi, I'm unloading/reloading a more or less large database (75GB). I understand that to optimize the reloading time I should do an ALTER DBSPACE on the new database file.

I was thinking on doing:

ALTER DBSPACE 60GB

But I was wondering whether this is going to take a very long time, and maybe it was more optimal to use a smaller size....

Do you guys have any comments about this?

This is an ASA9 database. At this moment I'm unloading/reloading in version 9, but hopefully in a couple of months I'm doing this again for ASA17.

Thanks, Edgard

[justin_willey]

This might be too obvious a point, but the biggest single factor in the speed is probably to avoid reading and writing to the same physical disk at the same time. So if you have two local disks available, have the new database on one and the old one on the other.

[Breck_Carter]

biggest single factor

Yes... in olden times, before giant RAM caches... like dbeng50 "By default, the database server usess (sic) 2 megabytes of memory for caching." 🙂

[VolkerBarth]

If the database file will become that large, it will be most efficient to grow the database file in one step. I would use the CREATE DATABASE DATABASE SIZE option for that.

Note that an unloaded database might be smaller than the original one (because of less free pages and morecompact row storage) so be sure the initial size is not "over-sized". It's often helpful to do a test unload to find out about the typical reload database size.

[Breck_Carter]

CREATE DATABASE ... DATABASE SIZE was added in Version 10.