1. ORA-00600/ORA-07445
Clause: Most likely it is related to bug
Solution: go to metalink and apply patch set.

2. ORA-03113
Clause: It is generic error means lots of reason behind this.
Solution: Depends on condition but best way to search on google/forms.

3. ORA-04031
Clause: Mis-configuration of SGA, insufficient memory
Solution: Sametime need to add memory on system, or sametime need to reduce SGA memory

4. ORA-12154
Clause: Wrong TNS_ENTRY is used.
Solution: Using NETCA tools configure tns entry or check tnsnames.ora file for correct entry.

5. ORA-12368
Clause: It is generic error lots of reason
Solution: Edit SQLNET.ORA and change NONE from NTS "SQLNET.AUTHENTICATION_SERVICES=NONE"

6. ORA-12500
Clause: It is generic error lots of reason
Solution: increase "processes" parameter, increase physical memory

7. ORA-12528
Clause: It is BUG in 10g (if you face this error in 10g)
Solution: Don't use TNS_ENTRY with connect string or edit listener configuration from STATIC to DYNAMIC.(search on my blog for more)

Common errors seen when using OUTER-JOIN

OUTER-JOIN is a very handy feature of SQL. But its value at solving certain classes of SQL query problems aside, it is also one of the most error prone Oracle SQL extensions we can put to use. Even advanced developers can make these mistakes. So let us discuss the error prone nature of this feature, and how to fix it.

For those who don't know what OUTER-JOIN is, here are our much over used friends DEPT and EMP with an illustration.

DEPTNO DNAME
---------- ----------
         1 Dept1
         2 Dept2

     EMPNO     DEPTNO ENAME
---------- ---------- ----------
111 PlainJane

 select d.*,e.empno,e.ename
from dept d,emp e
where d.deptno=e.deptno;

    DEPTNO DNAME           EMPNO ENAME
---------- ---------- ---------- ----------
         1 Dept1              11 PlainJane

 select d.*,e.empno,e.ename
from dept d,emp e
where d.deptno=e.deptno(+);

    DEPTNO DNAME           EMPNO ENAME
---------- ---------- ---------- ----------
         1 Dept1              11 PlainJane
         2 Dept2

Below are some question which everyone is confused

1. select count(*) or count(columname) which is faster ?
Answer: Both are same in performance in speed.

2. How frequently index should be rebuild.
Answer: NO, We never need to rebuild index becuase it is not increase database performance

3. For Oracle Database Windows is good OS or Linux is good.
Answer: Linux is much better than Windows for Oracle.

4. How to increase Database Performance?
Answer: Database performance use below methology.

1. Define what database performance is acceptable.
2. When you face performance related problem

Define where is come from means
1. it is related to Instance (SGA Configuration)
2. it is related to Client machine ( SYSTEM configuration)
3. it is related to Network delay

3. check database performance through
1. statspack report, awr report,tk*prof tools,sql trace etc.

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