Limit of the Number of Simultaneously Open Root Storage Files

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Applications that use StgOpenStorage() or StgCreateDocFile() API calls to open several storage files may fail.

This problem does not occur in Windows 95 or Windows NT 3.51.


Windows NT 4.0 limits the number of simultaneously open root storage files to around 500 PER PROCESS. It should be noted that this is a per process limit (for example, Process 1 can open 498 root storages, at the same time Process 2 can also open 498 root storages, and so on.)

Windows 95 and Windows NT 3.51, use a global shared memory heap of 64M; whereas Windows NT 4.0 uses a per-root-open heap of 4MB. Assuming a 2G user address limit for processes, Windows NT 4.0 supports around 500 root opens for a process.


On Windows NT 4.0 per-root-open heap size was further reduced to 2MB allowing around 1000 opens. A reduction in heap size means applications will not be able to open as many sub-storages or keep as many transacted changes uncommitted.


Microsoft has confirmed this to be a problem in Microsoft Windows NT version 4.0. This problem was corrected in the latest Microsoft Windows NT 4.0 U.S. Service Pack. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):


Article ID: 163202 - Last Review: January 9, 2015 - Revision: 1.1
  • Microsoft Windows NT Workstation 4.0 Developer Edition
  • Microsoft Windows NT Server 4.0 Standard Edition
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