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Article Code: N1
N1: What is the LDB file good for?
For every database opened for shared use, an .ldb file is created to store computer and security names and to place extended byte range locks. The .ldb file always has the same name and is located in the same folder as the opened database (.mdb or .mde).
When the last user closes a shared database, the .ldb file is automatically deleted. The only exception is if a user does not have delete rights for the folder, when the database is marked as corrupted or if ACCESS is not properly closed.
In these cases the .ldb file is not deleted because it contains information about who was using the database at the time the database was marked as corrupted. If you want to use database in a multi use environment then the .mdb file should be located in a folder where users have read, write, create and delete permissions. Even if you want users to have different file permissions (for example, some read-only and some read-write), all users sharing a database must have read, write, and create permissions to the folder. You can, however, assign read-only permissions to the .mdb file for individual users while still allowing full permissions to the folder.
If a user opens a database with exclusive access (by selecting the Exclusive check box in the Open dialog box), record locking is not used and ACCESS does not create an .ldb file. In this case the user needs only read and write permissions to the folder.
For each user opening a shared database, ACCESS writes an entry in the database's .ldb file. The size of each .ldb entry is 64 bytes. The first 32 bytes contain the computer name . The second 32 bytes contains the ACCESS login name. The maximum number of concurrent users is 255; therefore, the .ldb file size is never larger than 16 kilobytes.
When a user closes a shared database, his entry is not removed from the .ldb file. However, it may be overwritten when another user opens the database. This means that you cannot use the .ldb file to determine the current users of a database.
The ldb file information is used to prevent users from writing data to pages that other users have locked and to determine who has locked. If the Jet database engine detects a lock conflict with , it reads the .ldb file to get the computer and security name of the user who has the file or record locked.
In most lock conflict situations, ACCESS generates a Write conflict error message that allows the user to save the record, copy it to the Clipboard, or cancel the changes. In some circumstances, however, you receive the following error message:
Couldn't lock table TABLE NAME currently in use by user
USER NAME on computer COMPUTER NAME.
If you receive this message while you are the only user, then close the database and delete the orphan LDB-file.
The state of the information in the .ldb file has no influence on the state of the database. If an .ldb file becomes corrupted, everything in the database should still work correctly. However, you may see garbled text instead of user names in any lock conflict messages