MySQL
innoDBでは，16KBである．
The default InnoDB page size is 16KB.
https://dev.mysql.com/doc/refman/5.7/en/optimizing-innodb-diskio.html
PostgreSQL
8KBである．
The default value is 8192 bytes.
https://www.postgresql.org/docs/8.4/runtime-config-preset.html
Oracle
8KBである．
DB_BLOCK_SIZE
Default value 8192
https://docs.oracle.com/cd/B19306_01/server.102/b14237/initparams041.htm#REFRN10031
Microsoft SQL Server
64KBである．
The default value for SET BLOCKSIZE is 64.
https://docs.microsoft.com/en-us/sql/odbc/microsoft/set-blocksize-command?view=sql-server-ver15
IBM DB2
32KBである．
Use the default DRDA block size (32767) if it does not cause too much paging on executing your application.
https://www.ibm.com/docs/en/db2/11.5?topic=tuning-db2-connect-server
https://www.ibm.com/docs/en/db2/11.5?topic=tuning-db2-connect-server