[dba@soalinux ~]$ sqlplus sys/oracle@// as sysdba

SQL*Plus: Release Production on Thu Jun 7 12:58:17 2018

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Connected to:
Oracle Database 12c Enterprise Edition Release - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options

SQL> show parameter DB_BLOCK_SIZE

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_block_size                        integer     8192