# 查看当前会话
SQL> select
sid,
serial#,
username,
status,
program,
machine,
to_char(logon_time, ‘YYYY-MM-DD HH24:MI:SS’) as logon_time
from v$session
where username is not null
order by username;SID SERIAL# USERNAME STATUS PROGRAM MACHINE LOGON_TIME
———- ———- ———- ——– ——————————– —————— ——————-
123 45678 FGEDU ACTIVE sqlplus@fgedu.net.cn fgedu.net.cn 2026-03-31 09:00:00
124 45679 SYS INACTIVE oracle@fgedu.net.cn fgedu.net.cn 2026-03-31 08:00:00

# 查看活跃会话
SQL> select
s.sid,
s.serial#,
s.username,
s.status,
s.program,
s.sql_id,
s.event,
s.seconds_in_wait
from v$session s
where s.status = ‘ACTIVE’ and s.username is not null;SID SERIAL# USERNAME STATUS PROGRAM SQL_ID EVENT SECONDS_IN_WAIT
———- ———- ———- ——– ——————————– ————- —————————— —————
123 45678 FGEDU ACTIVE sqlplus@fgedu.net.cn abc123xyz000 db file sequential read 5

# 查看会话等待事件
SQL> select
s.sid,
s.serial#,
s.username,
s.program,
w.event,
w.wait_time,
w.seconds_in_wait,
w.state
from v$session s, v$session_wait w
where s.sid = w.sid and s.username is not null;

# 查看Top SQL（按CPU时间）
SQL> select
sql_id,
sql_text,
elapsed_time/1000000 as elapsed_sec,
cpu_time/1000000 as cpu_sec,
executions,
buffer_gets,
disk_reads
from v$sql
order by elapsed_time desc
fetch first 10 rows only;SQL_ID SQL_TEXT ELAPSED_SEC CPU_SEC EXECUTIONS BUFFER_GETS DISK_READS
————- ——————————————— ———– ———- ———- ———– ———-
abc123xyz000 select * from fgedu_employees where … 300.5 250.5 100 500000 10000

# 查看SQL执行计划
SQL> select * from table(dbms_xplan.display_cursor(‘abc123xyz000’));PLAN_TABLE_OUTPUT
——————————————————————————–
SQL_ID abc123xyz000, child number 0
————————————-
select * from fgedu_employees where employee_id = :1

Plan hash value: 1234567890

——————————————————————————–
| Id | Operation | Name | Rows | Bytes | Cost |
——————————————————————————–
| 0 | SELECT STATEMENT | | | | 2 |
| 1 | TABLE ACCESS BY INDEX ROWID| FGEDU_EMPLOYEES | 1 | 100 | 2 |
|* 2 | INDEX UNIQUE SCAN | PK_EMP_ID | 1 | | 1 |
——————————————————————————–

Predicate Information (identified by operation id):
—————————————————
2 – access(“EMPLOYEE_ID”=:1)

# 查看数据文件I/O
SQL> select
df.name,
fs.phyrds,
fs.phywrts,
fs.readtim,
fs.writetim
from v$datafile df, v$filestat fs
where df.file# = fs.file#
order by fs.phyrds desc;NAME PHYRDS PHYWRTS READTIM WRITETIM
————————————————– ———- ———- ———- ———-
/oradata/fgedudb/system01.dbf 100000 50000 500000 200000
/oradata/fgedudb/fgedu_data01.dbf 80000 60000 400000 300000

# 查看表空间I/O
SQL> select
ts.name,
sum(fs.phyrds) as phyrds,
sum(fs.phywrts) as phywrts,
sum(fs.readtim) as readtim,
sum(fs.writetim) as writetim
from v$tablespace ts, v$datafile df, v$filestat fs
where ts.ts# = df.ts# and df.file# = fs.file#
group by ts.name
order by sum(fs.phyrds) desc;NAME PHYRDS PHYWRTS READTIM WRITETIM
————————————————– ———- ———- ———- ———-
SYSTEM 100000 50000 500000 200000
FGEDU_DATA 80000 60000 400000 300000

# 查看系统等待事件
SQL> select
event,
total_waits,
time_waited,
average_wait,
time_waited_micro
from v$system_event
order by time_waited desc
fetch first 10 rows only;