Check Database Performance by these queries

SELECT * FROM v$log;

SELECT COUNT(*) FROM v$process;

SELECT COUNT(*) FROM v$session WHERE status='ACTIVE'

SELECT COUNT(*) FROM dba_locks WHERE blocking_others='Blocking';

SELECT COUNT(*) FROM dba_objects WHERE status='INVALID' AND owner IN ('ABC','DEF') GROUP BY owner;

SELECT A.Tablespace_Name,TRUNC((SUM(A.Tots)/1024/1024),3) Tot_Size,
TRUNC(((SUM(A.Tots)/1024/1024)-(SUM(A.Sumb)/1024/1024)),3) Tot_Used
FROM (
SELECT Tablespace_Name,0 Tots,SUM(Bytes) Sumb,
MAX(Bytes) Largest,COUNT(*) Chunks
FROM Sys.Dba_Free_Space A
GROUP BY Tablespace_Name
UNION
SELECT Tablespace_Name,SUM(Bytes) Tots,0,0,0
FROM Sys.Dba_Data_Files
GROUP BY Tablespace_Name) A, V$instance B
GROUP BY A.Tablespace_Name
ORDER BY A.Tablespace_Name

SELECT (1-(SUM(DECODE(name,'physical reads', value, 0))/
(SUM(DECODE(name,'db block gets', value, 0)) +
SUM(DECODE(name,'consistent gets', value, 0))))) * 100 "Read Hit Ratio"
FROM v$sysstat

SELECT d.status "Status",
d.tablespace_name "Name",
d.CONTENTS "Type",
d.extent_management "Extent Management",
TO_CHAR(NVL(a.bytes / 1024 / 1024, 0),'99G999G990D900') "Size (M)",
TO_CHAR(NVL(NVL(f.bytes, 0), 0)/1024/1024 ,'99G999G990D900') "Free (MB)",
TO_CHAR(NVL((NVL(f.bytes, 0)) / a.bytes * 100, 0), '990D00') "Free %"
FROM sys.dba_tablespaces d, (SELECT tablespace_name, SUM(bytes) bytes
FROM dba_data_files GROUP BY tablespace_name) a,
(SELECT tablespace_name, SUM(bytes) bytes
FROM dba_free_space GROUP BY tablespace_name) f
WHERE d.tablespace_name = a.tablespace_name(+) AND d.tablespace_name = f.tablespace_name(+)
AND NOT (d.extent_management LIKE 'LOCAL' AND d.CONTENTS LIKE 'TEMPORARY')
UNION ALL
SELECT d.status "Status", d.tablespace_name "Name", d.CONTENTS "Type", d.extent_management "Extent Management",
TO_CHAR(NVL(a.bytes / 1024 / 1024, 0),'99G999G990D900') "Size (M)",
TO_CHAR(NVL((a.bytes-t.bytes), a.bytes)/1024/1024,'99G999G990D900') "Free (MB)",
TO_CHAR(NVL((a.bytes-t.bytes) / a.bytes * 100, 100), '990D00') "Free %"
FROM sys.dba_tablespaces d, (SELECT tablespace_name, SUM(bytes) bytes
FROM dba_temp_files GROUP BY tablespace_name) a,
(SELECT tablespace_name, SUM(bytes_cached) bytes
FROM v$temp_extent_pool GROUP BY tablespace_name) t
WHERE d.tablespace_name = a.tablespace_name(+) AND d.tablespace_name = t.tablespace_name(+)
AND d.extent_management LIKE 'LOCAL' AND d.CONTENTS LIKE 'TEMPORARY'
ORDER BY 7