查看数据库信息

查看数据库的SQL 
1、查看表空间的名称及大小

set linesize 140;
set pages 200;
column tablespace_name format a30;

select tablespace_name,min_extents,max_extents,pct_increase,status from dba_tablespaces;

select tablespace_name,initial_extent,next_extent,contents,logging,extent_management,allocation_type
from dba_tablespaces
order by tablespace_name;

2、查看表空间物理文件的名称及大小

column db_block_size new_value blksz noprint
select value db_block_size from v$parameter where name='db_block_size';
column tablespace_name format a16;
column file_name format a60;
set linesize 160;
select file_name,round(bytes/(1024*1024),0) total_space,autoextensible,increment_by*&blksz/(1024*1024) as incement,maxbytes/(1024*1024) as maxsize from dba_data_files order by tablespace_name;

3、查看回滚段名称及大小

COLUMN roll_name   FORMAT a13          HEADING 'Rollback Name'
COLUMN tablespace  FORMAT a11          HEADING 'Tablspace'
COLUMN in_extents  FORMAT a20          HEADING 'Init/Next Extents'
COLUMN m_extents   FORMAT a10          HEADING 'Min/Max Extents'
COLUMN status      FORMAT a8           HEADING 'Status'
COLUMN wraps       FORMAT 999          HEADING 'Wraps'
COLUMN shrinks     FORMAT 999          HEADING 'Shrinks'
COLUMN opt         FORMAT 999,999,999  HEADING 'Opt. Size'
COLUMN bytes       FORMAT 999,999,999  HEADING 'Bytes'
COLUMN extents     FORMAT 999          HEADING 'Extents'

SELECT
    a.owner || '.' || a.segment_name          roll_name
  , a.tablespace_name                         tablespace
  , TO_CHAR(a.initial_extent) || ' / ' ||
    TO_CHAR(a.next_extent)                    in_extents
  , TO_CHAR(a.min_extents)    || ' / ' ||
    TO_CHAR(a.max_extents)                    m_extents
  , a.status                                  status
  , b.bytes                                   bytes
  , b.extents                                 extents
  , d.shrinks                                 shrinks
  , d.wraps                                   wraps
  , d.optsize                                 opt
FROM
    dba_rollback_segs a
  , dba_segments b
  , v$rollname c
  , v$rollstat d
WHERE
       a.segment_name = b.segment_name
  AND  a.segment_name = c.name (+)
  AND  c.usn          = d.usn (+)
ORDER BY a.segment_name;

4、查看控制文件

    select name from v$controlfile;

5、查看日志文件

    select member from v$logfile;

6、查看表空间的使用情况

select * from( select sum(bytes)/(1024*1024)  as "free_space(M)",tablespace_name
from dba_free_space
group by tablespace_name) order by "free_space(M)";

7、查看数据库库对象

    select owner, object_type, status, count(*) count# from all_objects
    group by owner,object_type,status;

8、查看数据库的版本　

     select * from v$version;

9、查看数据库的创建日期和归档方式

    select created,log_mode,log_mode from v$database;

10、查看临时数据库文件

    select STATUS, ENABLED, NAME from v$tempfile;

12 查看 SGA 内存大小
SQL> SHOW SGA;

Total System Global Area  524288000 bytes
Fixed Size                  1220336 bytes
Variable Size             155189520 bytes
Database Buffers          360710144 bytes
Redo Buffers                7168000 bytes
SQL> SELECT * fROM V$SGA;

NAME                      VALUE
-------------------- ----------
Fixed Size              1220336
Variable Size         155189520
Database Buffers      360710144
Redo Buffers            7168000