Nexus 9 is nearly unusable due to lag. - Google Product Forums

Nexus 9 is nearly unusable due to lag. - Google Product Forums

Thanks and welcome to the Nexus Help Forum.

If you recently installed any Lollipop updates, this may explain why your having some lag or performance issues with your Nexus 9. To fix it, try clearing out your cache and wiping your cache partition. This may restore any system files that is causing the performance issues. 

Clearing cached data

1. Go to Settings > Storage > Click on Cached data.
   
2. A message will pop up, "Clear cached data", choose Ok.
   
3. Restart Nexus.

If clearing the cache does not work, you may want to try wiping your cache partition

1. If you are not able to access the settings menu (such as when the device hangs when updating), use Recovery mode:
   
2. If your device is on, hold the Power button to restart the device.
   
3. When the device turns off, press and hold the Volume Down button, then press and hold the Power button at the same time until the tablet turns on.
   
Press the Volume Down button twice to highlight Recovery mode.

4. Press the Power button to start Recovery mode. You'll see an image of an Android robot with a red exclamation mark and the words "No command."
   
5. While holding down the Power button, press the Volume Up button.
   
6. Use the volume buttons to scroll to "wipe cache partition" then press the Power button to select it.
   
7. When the cache is cleared, press the Power button on "reboot system now."

If you still have issues downloading or installing a system update, try resetting your Nexus device to factory settings. Before doing any factory reset, I highly recommend you backup ALL important data on your Nexus.

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