TOO MANY PATTERN ATTEMPTS ON SAMSUNG GALAXY GT-P7100

Pattern Lock- Incorrectly enter pattern 5 times (4 or more points each time) . Pop up message will appear Click Next and you will be prompted for google a/c details or security question for pattern lock.
tap forgotten pattern and on next screen enter google account details. Then next screen allows you to choose a new screen lock option.

Otherwise for a factory reset use recovery mode
The only other solution is a hard reset which is only as a last resort. You need to access Androids Recovery mode. Check your manual. Most devices it is power off then power up holding volume + and power buttons.
Once in this mode use power down button to highlight "wipedata/factory reset option, then use power button to select it.
Vol - button to to scroll and select yes delete all user data option with power button. When device reset select option to reboot now and the device will turn on unlocked but you will have lost your personal data.