Merlon Software Corporation

Discover FAQ :

Disk is cheap, why do I need a disk management product?

You have to anticipate how each disk on the system will be used by your applications. It is not just a question of buying disk, it is knowing when you need to buy, and how the disk should be used to best advantage.

I have plenty of disk space already, why do I need a disk manager?

There are disk resource problems that can stop your applications running, even if there is lots of free disk space available. For example, a critical application file can become full, even if there is free space available on your disk.

How can I justify the cost of Discover to my management?

The first time Discover spots a potential problem before it happens and saves you an application outage, it will already have paid for itself. The cost of an outage for a typical application will dwarf the cost of Discover.

What makes Discover better than other products on the market?

Discover is quicker and easier to install.

It is quicker and easier to configure. There are no hard to understand tags and codes to select. You don't have to specify each file you want to monitor. There are no cryptic parameters and modes to specify when scanning disks.

The reports are easier to understand, and they run faster. (Discover does not use ENFORM).

Discover can be configured to automatically correct problems, not just report on them.

Discover SpaceMaker technology provides pro-active disk space management to help prevent extent allocation failures.

How much overhead does Discover take?

When Discover is not actively scanning, there is no impact of CPU usage. When it is actively scanning it uses a few percent of a CPU's cycles (less than 10 %). We recommend you run Discover at a low priority (for example 100). This will prevent it from interfering with your on-line applications.

There is special self-pacing code built into Discover that prevents it from "hogging" a CPU. Even if there is nothing else running in a CPU, Discover will not drive the CPU to more than about 10% busy.

Thus it is safe to run Discover when other system activity is going on. By using a low priority, and a self-pacing mechanism, we ensure Discover will not interfere with OLTP applications.

How long does it take Discover to scan the disks in a system?

There are two factors that will determine how long a scan will take.

The first factor is the number of files that are to be scanned. Obviously, the more files that must be scanned, the more time it will take. For planning purposes, you can estimate that Discover will scan about 400 files a minute. So, if a volume has 400 files on it, it will only take about a minute to scan, if it has 10,000 files, it will take about 25 minutes to scan. (Remember, you can select which disks you want Discover to scan, you don't need to scan all the disks on your system).

The second factor is system activity. If the system is very busy, Discover will be allocated fewer CPU cycles, so it will take longer to run. You can specify the time of day when scans should start, and how often they should be done. So for example, you can set up Discover to do one scan per day starting at midnight. You can start by running Discover at off-peak times until you get an idea of how it performs on your system.

Can I use Discover to predict my disk usage right away?

Discover makes predictions about disk and file usage based on historical data. It must have a chance to collect some data before it can start making predictions.

We recommend you allow two scan operations to complete before you start running reports, or using the TODO list features of Discover.

What kinds of problems can Discover detect?

Discover can detect many kinds of problems, including :

Disk volumes that are becoming full, or fragmented
Files that are becoming full
Files with unused space that can be freed up
Files with attributes that have changed (for example AUDIT, BUFFERED, OWNER)
Files marked as Corrupt, Broken, Crashopen, or Rollforward Needed.
Key sequenced files with too much slack and need to be reloaded
Key sequenced files that are disordered, and need to be reloaded
Users who are using too much disk space
Files owned by users who are no longer defined ("orphan files")

What kind of corrective actions can Discover take?

Discover can be configured to execute any TACL script, or program, such as FUP. So you can define the corrective actions that need to be taken. Examples include, FUP RELOAD to re-organize files, DCOM to defragment disks etc... You can also generate EMS alert messages to warn operation staff of problems.

What is SpaceMaker?

SpaceMaker is a technology to better manage disk space allocation. It automatically deallocates unused extents in files that are not growing, and preallocates extents to files that are growing.

Can Discover tell me which users are using up disk space?

Yes, Discover tracks disk usage on a user by user basis. You can set space quotas for users, and take automated actions when a user exceeds his quota.

Can Discover tell me when key sequence files need to be re-organized?

Discover can be configured to check key sequenced files for number of index levels, slack space and disorder. If a file has more than a configured number of index levels, or amount of slack space, or disordered data blocks, you can schedule a FUP RELOAD.

Some corrective actions like FUP RELOAD, or DCOM use a lot of system resources, can they be scheduled to run at off-peak times?

Yes. Discover uses a "TODO" list which supports scheduling of actions at specified time, for example at 2:00 am, or between 1:00 and 3:00 on Sunday morning.


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