Understanding D3/NT: VME and FSI
Both Dimensions and Spectrum have been discussing PICK's new D3/NT, yet sometimes it can be confusing on how and when to use its new features. I found this to be true when the dealing with the new D3 File System Interface (FSI). Initially, I was confused when trying to grasp the differences between the traditional Virtual Machine Environment (VME) and the new FSI. In this article I'll explain the difference between the VME and FSI.
What is the Virtual Machine Environment (VME)?
The VME is the traditional environment that you currently work with currently. It's the ABS frames, TCL prompt, the terminal interface, and other programs and functions you work with every day.
Since D3 is no longer an independent operating system like R83 and AP/Pro, a "virtual machine", or VME, is needed for the PICK OS to run. The VME allows you to access PICK information in a familiar environment. This VME has the same look and feel as the traditional environments we are used to seeing, but uses NT to do its I/O processes. People using the UNIX versions of Advanced Pick are already familiar with this concept.
With the VME using NT to do the I/O processes, you also get full use of the extra features that NT possesses: Network access, multi-processor support, and RISC processor support.
What is the D3 File System Interface (FSI)?
The D3 File System Interface is a new concept to the PICK operating systems. The FSI allows you to store your pick data outside traditional PICK file system, but still have the look and feel of a traditional PICK item.
Why would you use the FSI as opposed to the VME? The FSI allows your database to grow to an unlimited size. Due to the file size limitation in NT, the VME can only hold 1.5 Giga bytes of storage. Many existing system are larger than this or are pushing this limit. Since the FSI uses the NT's native file system, you are only limited to the size of the hard disk space on the NT computer.
Also, due to n-tier design of D3 you are no longer limited to one computer for storage. By making use of the network, you are able to use other computer's hard drives for free space.
By separating common files onto other servers, you are able divide heavy file accesses to separate computer and separate processors. In doing so, you can keep your system from grinding to a halt when accounting is doing year end reports or audits that use generic ACCESS selects on several thousand items.
The FSI will also allow you to take advantage of all the extras NT has in its file system: file privileges, transaction logging, and disk mirroring. You won't find these in the VME without programming on your part, or third party add-ons.
VME vs. FSI:
When would you use the VME? When would you use the FSI? In reality you can rely solely on the VME and never touch the FSI. You have all the functionality of your existing file system inside the VME, but the VME is limited by the amount of information it can hold.
With the FSI, you can create a true client/server system, which the VME cannot do. The one problem with the FSI is that it uses network resources to access information. As with all networks, the additional overhead will cause the information to be accessed slower than just accessing it from the hard drive. You'll have to decide if this draw back is worth the advantages of using the FSI.