Solr Index Lock Issue | Param's Blog

Solution
1. Delete the *.lock file manually and restart the Solr - This approach is quick and easy, Solr will be up and running again in seconds.
2. To resolve this issue for future problems:
Update solrconfig.xml to add below mentioned properties:

<mainIndex><unlockOnStartup>true</unlockOnStartup></mainIndex>

and It is recommended to use which avoids FS locks.

<lockType>simple</lockType> (1.3) 

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