你是问的是系统共享内存，还是SGA?

系统共享内存

–SGA 内存大小

SELECT a.SGA_MEM + b.PGA_MEM "TOTAL_MEMORY"
FROM  
( SELECT SUM(current_size) / 1024 / 1024 "SGA_MEM"
  FROM v$sga_dynamic_components,
  (
    SELECT SUM(pga_alloc_mem) / 1024 / 1024 "PGA_MEM"                    
     FROM v$process
   ) a
  WHERE component IN ('shared pool',
                               'large pool',
                               'java pool',
                               'streams pool',
                               'DEFAULT buffer cache')
   ) a,
(
  SELECT SUM(pga_alloc_mem) / 1024 / 1024 "PGA_MEM" FROM v$process
 ) b;

select component,
       current_size / 1024 / 1024            "CURRENT_SIZE_MB",
       min_size / 1024 / 1024                "MIN_SIZE_MB",
       user_specified_size / 1024 / 1024     "USER_SPECIFIED_SIZE_MB",
       last_oper_type                        "TYPE"
  from v$sga_dynamic_components;

select component, 
       granule_size / 1024 / 1024            "GRANULE_SIZE(Mb)"
  from v$sga_dynamic_components;
  
  
  SELECT component,
       parameter,
       initial_size,
       final_size,
       status,
       to_char(end_time, 'mm/dd/yyyy hh24:mi:ss') changed
  FROM v$sga_resize_ops
ORDER BY component;

SELECT component,
min(final_size) low,
(min(final_size / 1024 / 1024)) lowMB,
max(final_size) high,
(max(final_size / 1024 / 1024)) highMB
FROM v$sga_resize_ops
GROUP BY component
ORDER BY component;

SELECT name, bytes FROM v$sgainfo;

select * from v$sgastat order by bytes asc;