The memory for dynamic components in the SGA is allocated in the unit of granules. Granule size is determined by total SGA size. Generally speaking, on most platforms, if the total SGA size is equal to or less than 1 GB, then granule size is 4 MB. For SGAs larger than 1 GB, granule size is 16 MB. Some platform dependencies may arise. For example, on 32-bit Windows NT, the granule size is 8 MB for SGAs larger than 1 GB. Consult your operating system specific documentation for more details.

9i or earlier it was 4MB for sga_max size less than or equal to 128MB and 16MB for greater than 128MB. But from 10g it varies from platform as per documenation.

The memory for dynamic components in the SGA is allocated in the unit of granules. Granule size is determined by total SGA size. Generally speaking, on most platforms, if the total SGA size is equal to or less than 128 MB, then granule size is 4 MB. Otherwise, granule size is 16 MB.

However, there may be some platform dependency. For example, on 32-bit Windows NT, the granule size is 8 MB for SGAs larger than 128 MB. Consult your operating system specific documentation for more details.

Connected to:
Oracle9i Enterprise Edition Release 9.2.0.1.0 - Production
With the Partitioning, OLAP and Oracle Data Mining options
JServer Release 9.2.0.1.0 - Production

SQL> select component, granule_size/1024/1024 from v$sga_dynamic_components;

COMPONENT                                                        GRANULE_SIZE/1024/1024
---------------------------------------------------------------- ----------------------
shared pool                                                                           8
large pool                                                                            8
buffer cache                                                                          8

SQL> 

So, what do you want to do with that information? Why do you need to know for ALL platforms and versions and so on?

Regards
Michel

But why? There is a reason for your curiosity, you have something in mind.

Regards
Michel

In oracle 9i OCP exam book its stated that 4M and 16M,

SGA components are, with the exception of the log buffer, sized in granules.
A granule is an area of contiguous memory. The granule size is platform specific and
varies according to the total size of the SGA. Typical granule sizes are 4MB if the total
SGA is no bigger than 1000MB or 16MB if it is larger, but there are platform variations.
For instance, on Windows, the granule size is 8MB for an SGA greater than 1GB.