Multi-Volume DB

[toddt]

Here is an easy question for someone.

I recently converted our 8.3C single-volume database to multi-volume. I would like to keep an eye on the usage of the database extents so I can add another fixed length extent before the variable one starts being used. Where in promon can I find the info saying how much space in each extent is being used?

Somewhere in the R&D menu?

Thanks!

 

[Paavo Juntunen]

You can use promon option "7. Database Status"

Where you can compare "Total number of database blocks"
to "Database blocks high water mark".

-Pave-

 

[Norman Biggar]

You can also go to the "R&D" options on promon, choose "Status Displays", then "Database" and examine the values for "Empty Blocks".
This will show you both the number of empty blocks and the percentage of empty blocks.

 

[toddt]

Thanks for the fast response!

 

[mra]

Hi!

You're saying, you want to add another fixed extent before the dynamic extent is being used.


Note, that (in version 9) the variable extent will be closed (fixed) at the current size, when you add the new file - I'm not shure if this is true for version 8.

You'll end up with one very small extent!


We're just monitoring the size of the variable extent (from the OS). If it grows to large, we'll close the extent, and add another file.

Regards
Mike

 

[Norman Biggar]

Letting extents grow dynamically will affect your performance.

Whenever extra space requires to be written to, there will be a delay whilst the space is reserved prior to the writing being done.

toddt's principal of monitoring the fixed extents so that a new fixed extent is added before the variable one is used is the best method.

Avoid variable extents wherever possible.

 

[mra]

Hi!

True!

Can you quantify the performance impact? It is after all at most 128 * 8Kb each time.

Our problem is uptime, the time required to create 1Gb of data extent is unacceptable for most of our clients.


Regards
Mike

 

[Norman Biggar]

I think we're moving away from the initial topic.

Suggest you might consider posting a topic "What performance benefits gained from fixed extents".

However, Progress KB10759 describes the performance difference as "significant".

Your strategy might be forced upon you by your users, but it isn't the one that Progress recommend.