Hello Amukesh83....

Solution 1: Restart your computer

The most common causes of this error are another program using the file or a problem with the file that was caused when the computer was shut off unexpectedly (like a power failure). The good news is that most of the time, simply restarting your computer and then restarting Firefox is the fix for both problems.

Solution 2: Create a new database

If restarting your computer doesn’t take care of things, you can fix this by having Firefox create a new places and favicon database for you. Don’t worry, it’s not as hard as it sounds.

Part 1 – Open your profile folder

*  From the Help menu, select Troubleshooting Information. The Troubleshooting Information tab will open.
*  Under the Application Basics section next to Profile Folder, click Show in Finder. A window will open that contains your profile folder.

Part 2 – Create a new database

1. (Optional) Create a bookmark backup file.
2. Click the Firefox menu at the top of the screen and select Quit Firefox. Wait until Firefox has completely quit.
3. In the Firefox profile folder, find and delete (or rename) the favicons.sqlite and places.sqlite files.

     * You can rename instead of deleting a file, to keep it as a backup. Click on it once to select it, click a second time on the file name to make it editable, then add .old to the end of its name. 

4. Also delete the favicons.sqlite-shm, favicons.sqlite-wal, places.sqlite-shm and places.sqlite-wal files, if they exist. 5. Finally, reopen Firefox.

      *  When Firefox reopens, it will create new favicons.sqlite and places.sqlite database files. Your browsing history will be lost but Firefox will automatically restore your bookmarks from the most recent bookmarkbackups file.
     *   If your bookmarks weren’t restored, try the steps in the Recover lost or missing Bookmarks article.

If you have sync, and there is a problem anywhere, Shut Down Sync Immediately On All Devices to prevent the problem from spreading. Once the problem is fixed, perform the same repair on all computers/profiles before using sync again.

[v57+] Places Maintenance is built into Firefox.

Type about:support<enter> in the address bar.

You will find Places Database near the bottom. Press the Verify Integrity button.

When done, copy and post the results here.

See also:

• https://support.mozilla.org/en-US/kb/fix-bookmarks-and-history-will-not-be-functional