Recovery After a Crash
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Recovery After a Crash

Beginning with version 3.20 of WinDaq Acquisition software, Event Markers, Comments, and Channel Annotations may be recovered following a system failure.


Perform the following steps to recover data after a system failure:

  1. Open the main file in WinDaq Acquisition by clicking on File > Open.
  2. When asked "File already exists. Do you want to append to it?" answer Yes.
  3. If the file has no trailer data you will be asked: "Was ScanDisk run after power failure or crash to avoid data loss in file <name>?" or "Were file system errors fixed on drive with file <name> after failure or crash?" If ScanDisk (or its equivalent) was not run you may do so now if desired (ScanDisk is necessary if you suspect that the directory length of the main file is too short for the data acquired before the failure; for systems without ScanDisk go to My Computer, highlight the hard disk drive and click on File > Properties > Tools > Check Now > Automatically Fix File System Errors > Start with "Scan for and attempt recovery of bad sectors" unchecked). Answer Yes to either of the above questions.
  4. If the file has no data, recovery will fail with the message: "No data was physically written to file <name> before the failure." All files are left intact to allow for a recovery. Run ScanDisk or equivalent.
  5. Click on File > Record to append the file. If you will not acquire more data, click on File > Close.


Note: If Edit > Preferences > Write Through was not checked, up to a cluster of garbage data instead of just 256 samples may be displayed at the end of the file. This may be removed in WWB (Version 2.49 and above) by setting Edit Compression to 1, moving the cursor to the last good data value, checking Options > Set Time Marker, using Ctrl+Home to move to start of file, and using File > Save As in format 2 to output to a different filename.


Starting with V3.20 WinDaq NT-style software, in addition to writing A/D converter data following a header to a main file (usually .WDQ or .WDH), WinDaq also writes to additional side files with the following extensions:


WDE     Event Markers, timestamps, and comment pointers

WDN     Event Marker Comments

WDU     User Annotation


Data is written to these files each time an event marker is generated or User Annotation is edited. If the new menu item Edit Preferences Write Through is checked, the directory on disk is updated each time an event or comment is generated, and each time A/D converter data is written to the main file about every 256 samples. This should not be used at high speeds because it generates enough disk activity to significantly slow down the maximum sample rate for gap-free recording to disk or affect the performance of other applications. However, in the event of a power failure or crash, it eliminates the need to run ScanDisk or its equivalent to update the directory before recovering the file.


The old menu item Edit > Preferences > Event Mark Capacity has been deleted from NT-style software, since the number of event markers allowed per manual start is now limited only by available disk space.


Windows 95/98 users of the parallel port interface or DI-400 series cards must install new_zq.exe or new_wme.exe NT-style software to benefit from this feature. This will limit the maximum sample rate through an EPP parallel port to about 110,000 samples/sec even if Edit Preferences Write Through is not checked. Because Windows 95/98 does not support opening files with the FILE_SHARE_DELETE flag, if WWB is looking at a file when it is closed by acquisition, WinDaq will silently fail to delete the side files. If WWB is still looking at the file when acquisition tries to reopen it for append, the open request will be refused.