Db_cache_size and shared_pool_size initialization parameters are 0 ?!

It is strange that when we query db_cache_size today, we find that the value is 0. Later, we checked some sharing areas, and it was actually 0.

SQL> show parameter db_cache_size
Name type value
---------------------------------------------------------------------------------------------------
Db_cache_size big integer
0

SQL> show parameter shared_pool_size
Name type value
---------------------------------------------------------------------------------------------------
Shared_pool_size big integer
0

SQL> show parameter pool
Name type value
---------------------------------------------------------------------------------------------------
Buffer_pool_keep string
Buffer_pool_recycle string
Global_context_pool_size string
Java_pool_size big integer 0
Large_pool_size big integer 0
Olap_page_pool_size big integer 0
Shared_pool_reserved_size big integer 22649241
Shared_pool_size big integer 0
Streams_pool_size big integer
0

Later, through the wh62592855 blog.

The db_cache_size parameter described in references has the following sentence:

Default Value

IfSGA_TARGETIs set: If the parameter is not specified, then the default is0(Internally determined by the Oracle database). If the parameter is specified, then the user-specified value Indicates a minimum value for the memory pool. IfSGA_TARGETIs not set, then the default is either 48 MB or 4 MB * Number of CPUs, whichever is greater

Because a 10 Gb assm is used to automatically share memory management, Oracle will automatically allocate space to each pool, so its value is 0.

Check whether the system automatically adjusts these parameters at a specific time point.

Select X. ksppinm name, Y. ksppstvl value, X. ksppdesc describ
From SYS. x $ ksppi X, SYS. x $ ksppcv y
Where X. inst_id = userenv ('instance') and Y. inst_id = userenv ('instance') and X. indx = y. indx and X. ksppinm like '% pool_size % ';

NAME value
Describ

Certificate --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
_ Numa_pool_size not specified aggregate size in bytes of NUMA pool
_ Shared_pool_size
452984832 actual size in bytes of Shared Pool
Shared_pool_size 0 size in bytes of Shared Pool
_ Large_pool_size 16777216
Actual size in bytes of large pool
Large_pool_size 0 size in bytes of large pool
_ Java_pool_size 16777216
Actual size in bytes of Java pool
Java_pool_size 0 size in bytes of Java pool
_ Streams_pool_size 0
Actual size in bytes
Of streams pool
Streams_pool_size 0 size in bytes of the streams pool
_ Io_shared_pool_size 4194304 size of I/O buffer pool from SGA
_ Backup_io_pool_size 1048576 memory to reserve from the large pool
Global_context_pool_size global
Application context pool size in bytes
Olap_page_pool_size 0 size of the OLAP page pool in bytes
Select X. ksppinm name, Y. ksppstvl value, X. ksppdesc describ
From SYS. x $ ksppi X, SYS. x $ ksppcv y
Where X. inst_id = userenv ('instance') and Y. inst_id = userenv ('instance') and X. indx = y. indx and X. ksppinm like '% db_cache_size % ';

Name valuedescrib
Certificate --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
_ Db_cache_size 1644167168 actual
Size of default buffer pool for standard block size buffers
Db_cache_size 0 size of default buffer pool for standard block size buffers

* Parameters starting with two underscores determine the current SGA allocation and are also parameters for dynamic memory management and adjustment. Changes to these parameters will be recorded in the spfile file and will remain valid at the next database startup.

The new dynamic view v $ sga_dynamic_components added by Oracle 10 Gb allows you to view the time and type of adjustment for each dynamic component.

Select component, current_size, min_size, last_oper_type, last_oper_mode, to_char (last_oper_time, 'yyyy-mm-dd hh24: MI: ss') Lot
From v $ sga_dynamic_components;

Component
Certificate ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Current_size min_size last_oper_type last_oper_mode lot
-------------------------------------------------------------------------------------------------------------------------------------------------
Shared Pool
452984832 452984832 static
Large pool
16777216 16777216 static
Java pool
16777216 16777216 static
Streams pool
0 0 static
Default buffer cache
1644167168 1644167168 initializing
Keep buffer cache
0 0 static
Recycle buffer cache
0 0 static
Default 2 K buffer cache
0 0 static
Default 4 K buffer cache
0 0 static
Default 8 K buffer cache
0 0 static
Default 16 K buffer cache
0 0 static
Default 32 K buffer cache
0 0 static
ASM buffer cache
0 0 static