WD97: How Word for Windows Uses Temporary Files (89247)

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Definition of a Temporary File

A program creates a temporary file to temporarily store information. The program determines where and when to create temporary files. Temporary files are available only for the current session of the program.

Why Does Word Create Temporary Files?

Speed:

Word sometimes copies portions of a file into memory so that it can access the information more quickly when you copy and paste or scroll through a document. Word references the location of the information instead of actually accessing the information, which reduces the time Word spends performing these functions.

Data Integrity:

Word's uses temporary files as a "safety net" to protect against system errors in its file saving scheme. By saving to a temporary file first and then renaming the file to the proper name, Word ensures the data integrity of your original file against problems (such as a power failure or lost network connections) that might occur while the file is being written.

Types of temporary files

MS-DOS-Based File:

These are standard MS-DOS files.

Document File Based File:

The difference between this file and a traditional MS-DOS file is that multiple programs can read and write to these files without the original owner knowing about it. Additionally, document files have inherent properties that allow Word to create files and directories within files. At startup, Word creates one temporary (direct) document file called ~wrfxxxx.tmp. You can determine that it is a document file because the initial size is 1536 bytes. This temporary document file is used to store all OLE objects belonging to unnamed documents, undo, the Clipboard, and to documents whose native formats are not document format (for example, .txt, .rtf, and Word 2.0 documents). Word can open document files using two different modes: transacted and direct. These modes are discussed later in this article.

Transacted Document Files:

Transacted files allow Word to open a file, write to it, and have other programs--such as Microsoft Excel--write to it, but still retain the right to restore the file to the state it was in when Word first opened it.

To do this, the document file creates ghost images (typically ~dftxxxx.tmp) of all the changes made to the file after it was opened; if Word keeps all the changes, the contents of ~dftxxxx.tmp merge with the original file, and then saves a complete version of it. On the other hand, if Word discards all changes, then ~dftxxxx.tmp is deleted, and the original file does not change. Word opens all of the Word native files using transacted files, which create ghost images in the Temp directory. When you start Word, Normal.dot is typically opened in transacted mode, and a ghost file is created for it called dftxxxx.tmp. FastSave, for example, merges these two files when a save occurs.

Direct:

Word uses direct storage when opening the temporary document file and when performing either a Save As or a Full Save (non-FastSave save). This type of file is a low (if any) consumer of memory and does not create a ghost image when created or opened.

Specific Files That Word Creates

The following tables list some of the specific temporary files that Word creates.

   Files typically created when Word is started                File name
   ------------------------------------------------------------------------
   MS-DOS-based file (to reserve 4 file handles) 0 bytes      ~wrf0000.tmp
   MS-DOS-based scratch file                     0 bytes      ~mfxxxx.tmp
   Compound file - transacted                    0 bytes      ~dftxxxx.tmp
   Compound file - direct                        1536 bytes   ~wrf0001.tmp
                   (unnamed non-Word/OLE files)


   Word recovery files                                        File name
   -----------------------------------------------------------------------
   Temporary file for AutoRecovery                         ~wraxxxx.tmp
   AutoRecovery                                    AutoRecovery save of 
                                                   <docname>.asd


   Other Word temporary files                                 File name
   -----------------------------------------------------------------------
   Copy of another document                                   ~wrcxxxx.tmp
   Word document                                              ~wrdxxxx.tmp
   Temp document file                                         ~wrfxxxx.tmp
   Dictionary                                                 ~wrixxxx.tmp
   Clipboard                                                  ~wrlxxxx.tmp
   Macro                                                      ~wrmxxxx.tmp
   Word OLE document                                          ~wroxxxx.tmp
   Scratch file                                               ~wrsxxxx.tmp
   Converted (foreign) document                               ~wrvxxxx.tmp
				

A Simplified View of the Scheme Used to Save an Edited File

Create temp file                     Create ~wrdxxxx.tmp
Write temp file                      Save example data to ~wrdxxxx.tmp
Delete original file                 Delete EXAMPLE.DOC
Rename temp to target name           Rename ~wrdxxxx.tmp to Example.doc
				

Word gains significant performance speed by placing the temporary file in the same directory as the saved file. If Word placed the temporary file elsewhere, it would have to use the MS-DOS COPY command to move the temporary file from the other directory to the saved location. By leaving the temporary file in the same directory as the saved document file, Word can use the MS-DOS MOVE command to quickly designate the temporary file as the saved document.

When and Where Word Creates Temporary Files

The location of where Word creates the temporary files is hard-coded information and cannot be edited. In general, Word creates temporary files for the following types of data.

Embedded Word Objects (Temp Directory):
When Word acts as an OLE server program, the embedded Word objects are stored as temporary files in the Temp directory.

OLE 2.0 requires extra drive storage. When you start OLE programs, Word needs to provide copies of the data to the server. It is not unusual for extensive OLE 2.0 usage in a single session of a program to accumulate a large amount of temporary storage on the hard drive.

Scratch File (Temp Directory):

When Word runs out of internal random access memory (RAM), it always creates a single temporary scratch file in the Temp directory to hold information. This scratch file holds information that is swapped out from the Word internal file cache, which is allocated from global system memory. The scratch file varies in size from 64 kilobytes (KB) to 3.5 megabytes (MB). You can prevent Word from having to write to the scratch file by allocating more RAM for Word to use internally.

The default cachesize in Word is 64 KB.

For more information about increasing the cachesize in Word, please see the following article in the Microsoft Knowledge Base: Recorded Macro (Temp Directory):

When you record a macro, Word creates a temporary file in the Temp directory.

Converted Files (Temp Directory):

The word processor converters supplied with Word create temporary files in Rich Text Format (RTF), which Word uses to access specific converters.

Locked Files (Temp Directory):

When you open a file that is locked, either because it is open in another window of Word or because another user on the network has it open, you can work with a copy of the file. Word places this copy in the Windows Temp directory. Likewise, if a template attached to a document is locked, Word automatically makes a copy of the template in the Temp directory. The copy of a locked file does not automatically update the original owner's file.

Saved Files (Same Directory as the Saved File):

When you click Save on the File menu, the following happens: Text Pasted Between Files (Same Directory as Source File):

When Word copies and pastes between documents, it may create a temporary file in the same directory as the source file--especially if the source file is saved or closed. The temporary file represents the information that was referenced by the Clipboard prior to saving the file. Word creates this temporary file by renaming the old copy of the file to a temporary file name.

Owner File (Same Directory as Source File):

When a previously saved file is opened for editing, printing or review, Word creates a temporary file with a .doc file name extension that begins with a tilde "~" followed by a dollar sign "$" followed by the remainder of the original file name. This temporary file holds the logon name of person opening the file and is known as the "owner file." When you attempt to open a file that is available on a network and is already open by someone else, this file supplies the <user name> for the following error message:







Word automatically deletes this temporary file when the original file is closed from memory.

Automatic Save:

Word 97 Auto Recover Save Directory:

The Location of Temporary Files When You Close a File

Word may occasionally have to maintain a link to a file after it is closed. This occurs when text has been copied to the Clipboard from the file. When you close a file, Word attempts the following actions:

• If the selection that was copied to the Clipboard does not contain multiple sections or a picture, or is not large, Word copies the piece of the document to the scratch file.
• If the copied selection does contain pictures or multiple sections, or if the file is on a floppy disk, Word copies the entire file to the Temp directory and moves the pointer there.