check-oracle-db-blocksize
[dba@soalinux ~]$ sqlplus sys/oracle@//192.168.56.102:1521/pdbsoa as sysdba

SQL*Plus: Release 12.1.0.2.0 Production on Thu Jun 7 12:58:17 2018

Copyright (c) 1982, 2014, Oracle.  All rights reserved.

Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 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
SQL>