Hello,
What should I look in the report to see the available and unavailable space in DB?
What is the stage we should increase the datasize? Any rule of thump
Thanks
ADAREP and AOS both have sections to provide unused storage extents. You can always total that and divide by the total database size to get a percentage free.
As for rule of thumbs, it’s all what you’re comfortable with. Some like a lot of space for growth, while others manage by knowing exactly what they need and don’t worry about free space extents.
I’ll tell you what I did pre-version 8. I would reorder files when they hit 4+ extents. I would typically perform a reorder once every 2 months or so of the handful of such files. When it got to the point where I would perform the reorder and need to do another one the next 1-2 weeks already, I would know that the available extents were getting to be too small and thus the free space was becoming exhausted and I would need to add space. Typically, if I made a good request forecast, it would be about 1 year before I would need to ask again for more packs to be clipped.
In version 8, it’s no longer required to reorder files at 4+ extents, so going back to the top of this post, knowing the percent free is important. The other important factor is to know the rate your space is being allocated to files (the rate your free space percent is falling). This will allow you to forecast approximately when you’ll be out of space, so it’s best to add space before then!
The rule of thumb would depend on two things:
a) how fast your files grow
b) how easy it is for you get a maintenance window to do the increase.
For production I would start with free space at around 10%, and aim to increase the database once per year. Until you have a feel for how quickly the free space is getting used, best to check the percentage weekly at first, then monthly. Make sure the applications people know that they should tell you if they are going to dramatically increase the volume of data.
Some conservative or fast growing sites might want 20% free space for production. Other large databases but slow-growing databases might be OK with 5%.
For non production I am happy with 1-5% free space since I can increase at short notice.
If I have a critical space shortage and no chance for an outage to increase, the quickest way to temporarily relieve the problem is to deallocate some space from a file that doesn’t need it. But soon after this, I know it’s time to do an increase.
We tend to keep our databases with about 10% free space, 5% for the very large databases. One technique is to run Adareps on a regular basis (suggest to output them to an xml format) and upload that data to an Adabas file that stores date, asso and data free space; and also by file space and free space. With this data, you can chart when you may need to increase.
We also have done frequent reordering to manage space; however, I have done several performance studies where the reordering degrades performance. Reordering tends to only help space. This is a very generic statement.