Update README

README.md

@@ -1,13 +1,14 @@
-pg_checksums - Activate/deactivate/verify checksums in offline clusters
-=======================================================================
+pg_checksums - Activate/deactivate/verify checksums in PostgreSQL clusters
+==========================================================================
 
 `pg_checksums` is a small tool based on the `pg_verify_checksums` program
 available in PostgreSQL from version 11 on. In addition to verifying checksums,
 it can activate and deactivate them.  The former requires all database blocks
 to be read and all page headers to be updated, so can take a long time on a
 large database.
 
-The database cluster needs to be shutdown cleanly in order for the program to
-operate.
+The database cluster needs to be shutdown cleanly in the case of checksum
+activation or deactivation, while checksum verification can be performed
+online.
 
 PostgreSQL versions since 9.3 are supported.