Fractured files

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EFFICIENT use of your TI disk system... although the TI does use its disks quite efficiently, knowing what it does can help you to obtain the best from it.

When you place a program (say) onto the disk, the controller looks at the disk index for unused space, and places your program there, marking the index accordingly. Although the disk manager will show you your files in alphabetical order, they actually occur on the disk in the order they are recorded .... assuming a blank disk to start that is.

Suppose you have a long file called XXX which you replace with a shorter file, also called XXX? The new recording will go over the old XXX and the space saved will be MARKED as available ( actually the data is still on the disk!). Subsequently you save a very long file YYY. Part of YYY may be placed in the 'saved' space no longer needed for XXX, and another part of the file may be found after file ZZZ... we then refer to file YYY as a FRACTURED FILE.

The disk controller looks at the index, deals with the first part of the file, and then moves the drive head to the next part of the file. This movement can be thought of as wasted time: it is faster and more efficient if files are NOT fractured.

Now take another disk with files A, B and C, recorded in that order. We wish to amend File A, making it longer... the extra will be placed after File C, and File A will again be fractured.

SO .... how to put files together? When you use the DISK MANAGER to copy a disk using BACKUP DISK and copy to a blank disk, the module/controller will record the new disk with entire (unfractured) files, placed on the disk in alphabetical order.

Efficiency hint number one: Fractured files are best healed!

You have noted that when copying files with BACKUP DISK the files are placed onto the new disk in alphabetical order?

This may not be the best thing for us!!! Suppose our disk has a LOAD file which is used frequently? The best place for a file used often is at the beginning of the disk, while rarely used files are best at the end of the disk. We can place files just where we want them by taking a blank disk, and using COPY FILE to place them onto the copy disk in the order we want.

As an example, let's look at MULTIPLAN .... when working with Multiplan, the system makes frequent reference to the file called OVERLAY, while files MPCHAR, MPDATA, MPINTR and MPBASE are used only when you start using Multiplan.

Your disk system can use Multiplan more effectively then if the files are copied in the order OVERLAY, MPHLP, MPCHAR, MPDATA, MPINTR and MPBASE.

Efficiency Hint Number Two: Files are stored on a disk in the order recorded: the further the files are from the disk directory the longer the 'head seek' times.

If you use any of the SECTOR COPIERS now available (including TI Forth) the copy disk will be identical to the master: fractured files will NOT be repaired... but if you have manipulated file order, that order will be retained.