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-
- JP Software
-
- SDFLUSH Documentation
-
- Version 1.0 -- December 16, 1993
-
-
- Copyright 1993, JP Software Inc., All Rights Reserved. Published by JP
- Software Inc., P.O. Box 1470, E. Arlington, MA 02174 USA, (617) 646-3975,
- fax (617) 646-0904.
-
-
- This file explains how to use SDFLUSH, JP Software's TSR utility for use
- with 4DOS and SMARTDRV.
-
- Microsoft's SMARTDRV disk cache program offers a "delayed write" or
- "write-behind" mode. In this mode, data written to disk is held in the
- cache (in memory) until the system is idle (or until the cache memory area
- is full), at which point the data is physically written to the disk.
-
- This approach can improve performance, but it can also be dangerous -- for
- example, if you wait for the prompt and then turn off the computer, there
- may be data in the cache which has not yet been written to disk.
-
- Under PC-DOS 6.1 and MS-DOS 6.2, COMMAND.COM attempts to minimize this
- danger by instructing SMARTDRV to write all cached data to the disk before
- the command prompt is displayed.
-
- 4DOS does not currently interact with SMARTDRV in this way. However, if you
- wish to enable this behavior under 4DOS you can do so with SDFLUSH.
-
- SDFLUSH is a TSR which watches for a signal from 4DOS indicating that 4DOS
- is about to display a prompt. It then sends the appropriate signals to
- instruct SMARTDRV to write cached data to the disk. It does not allow 4DOS
- to display the prompt until it receives an indication from SMARTDRV that
- there is no more data waiting to be written to the disk.
-
- Note that you do NOT need SDLFUSH unless (a) you are using SMARTDRV from
- MS-DOS or PC-DOS version 6 or later, (b) SMARTDRV is running in
- delayed-write mode, and (c) you wish to force cache data to be written to
- disk before each prompt is displayed.
-
- To use SDFLUSH, simply load it with a command like this:
-
- c:\> c:\4dos\sdflush
-
- Normally you would place this command in AUTOEXEC.BAT or otherwise load it
- when your system boots. SDFLUSH should be loaded after SMARTDRV. It can
- be loaded high with the LH command or other similar utilities if you wish.
- SDFLUSH uses 336 bytes when resident in memory.
-
- SDFLUSH cannot unload itself, but you can unload it with MARK and RELEASE
- from the TSRCOM utility package (available on-line or on the 4DOS Utility
- Disk from JP Software), or other similar TSR management utilities.
-
- SDFLUSH works with PC-DOS 6.1 and MS-DOS 6.2 as described above. In
- addition, SDFLUSH will work with MS-DOS 6.0 SMARTDRV. You may find this to
- be an improvement over MS-DOS 6.0 COMMAND.COM, which does not offer a
- similar feature.
-
- SDFLUSH is designed for use with 4DOS 5.0 and above, along with SMARTDRV
- for MS-DOS / PC-DOS version 6.x. If you do not have both 4DOS and SMARTDRV
- loaded, there is no point in loading SDFLUSH. SDFLUSH may work properly
- with SMARTDRV from MS-DOS / PC-DOS version 5, and with 4DOS version 4, but
- it has not been tested in those environments.
-
- Some other cache software responds to the same signals as SMARTDRV and may
- therefore work properly with SDFLUSH, but we have not tested such
- combinations and cannot guarantee the results.
-
- CAUTION: USING ANY CACHE PROGRAM IN DELAYED WRITE MODE CAN REDUCE THE
- INTEGRITY OF YOUR SYSTEM. If you use SMARTDRV or any other cache program
- in delayed write mode we STRONGLY encourage you to use your own methods to
- ensure that the cache is empty prior to rebooting or shutting down your
- system, defragmenting your hard disk, or disabling your cache. Such
- methods might include issuing the appropriate "flush buffers" command for
- your cache software (for example, the SMARTDRV /C command), or observing
- the disk activity light for an appropriate period of time to ensure that
- activity has ceased.
-
- JP Software cannot guarantee that SDFLUSH will provide additional safety on
- your particular system. SDFLUSH is a relatively simple program and we
- expect it to work reliably. We have tested it with SMARTDRV under MS-DOS
- 6.0 and 6.2 and found that it does delay display of the prompt until cached
- writes are completed. However this behavior may change due to interaction
- with other memory-resident programs, updates to SMARTDRV, and any SMARTDRV
- configuration options you select. Therefore you may wish to use the
- additional methods as described above to help ensure that cached data is
- written to disk when such assurance is required.
-
- DISCLAIMER: THIS SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY
- KIND. IN NO EVENT SHALL WE BE LIABLE FOR ANY INCIDENTAL, CONSEQUENTIAL, OR
- PUNITIVE DAMAGES WHATSOEVER ARISING OUT OF USE OF THIS PROGRAM.
-
- SDFLUSH is distributed free of charge by JP Software, and may be
- redistributed freely, as long as this documentation and the program itself
- are included with all copies, and have not been altered in any way.