1、Oracle数据库的登录：

1、登录到数据库服务器

2、登录到SQLPlus

sqlplus / as sysdba

3、【可选】连接要具体操作的用户

conn 用户名/密码

数据查询

1、查看并发连接数

select machine,count(*) from gv$session group by machine;

2、查看日志表空间：

SELECT Upper(F.TABLESPACE_NAME),
D.TOT_GROOTTE_MB,
D.TOT_GROOTTE_MB - F.TOTAL_BYTES,
To_char(Round(( D.TOT_GROOTTE_MB - F.TOTAL_BYTES ) / D.TOT_GROOTTE_MB * 100, 2), '990.99')
|| '%' ,
F.TOTAL_BYTES,
F.MAX_BYTES 
FROM (SELECT TABLESPACE_NAME,
Round(Sum(BYTES) / ( 1024 * 1024 ), 2) TOTAL_BYTES,
Round(Max(BYTES) / ( 1024 * 1024 ), 2) MAX_BYTES
FROM SYS.DBA_FREE_SPACE
GROUP BY TABLESPACE_NAME) F,
(SELECT DD.TABLESPACE_NAME,
Round(Sum(DD.BYTES) / ( 1024 * 1024 ), 2) TOT_GROOTTE_MB
FROM SYS.DBA_DATA_FILES DD
GROUP BY DD.TABLESPACE_NAME) D
WHERE D.TABLESPACE_NAME = F.TABLESPACE_NAME
ORDER BY 1;

3、查看日志表空间目录：

select tablespace_name,
file_id,
file_name,
round(bytes / (1024 * 1024), 0) total_space
from sys.dba_data_files
order by tablespace_name