Oracle ASH report introduced on Oracle 10GR2. It is kind of statistical data collected by Oracle Sampled data. The sampling is done on the current active sessions. Sampled data collected to circular buffer in SGA and the same can be accessed through V$ views. V$ACTIVE_SESSION_HISTORY view provides the sampled session activity for the instance.
Fix ORA-02299: cannot validate (SCOTT.EMP_UK) - duplicate keys found
Error Description:
Unique key constraint creations failed on table with following error.
SQL> alter table emp add constraint emp_UK unique (emp_id);
alter table emp add constraint emp_UK unique (emp_id)
*
ERROR at line 1:
ORA-02299: cannot validate (SCOTT.EMP_UK) - duplicate keys found
Retrieve / Recover / Restore Dropped Table in Oracle 10g 11g Using Flashback Table Feature
Suppose by mistake if you drop a table in Oracle 10g Oracle 11g you can retrieve the table using Flashback table feature. Flashback feature works with recycle bin to recover the table. For this the recycle bin must be enabled for the database.
How to Drop Oracle 10g 11g Bin$ / Recycle bin Tables
In Oracle 10g and 11g if you do a select * from tab; you can see many tables starts with Bin$ which we cannot drop using drop table command. These are the objects in the recycle bin which can be used for recovery purpose in case needed.
SQL> select * from tab;
Oracle Kill Session Command Fails with ORA-00027: cannot kill current session
Error Description:
DBA is trying to kill oracle sessions and one session is getting failed with following error.
SQL> alter system kill session '786,53315';
alter system kill session '786,53315'
Oracle Create table, Materialized View Command Fails with ORA-01723: zero-length columns are not allowed
Error Description:
Oracle Create As Select Command (CTAS) failed with following error.
SQL> create table emp as select name, null age from candidate;
create table emp as select name, null age from candidate
*
ERROR at line 1:
Public Database Link fails with ORA-12154: TNS:could not resolve the connect identifier specified
Error Description:
Select from database link fails with following error.
12154. 00000 - "TNS:could not resolve the connect identifier specified"
*Cause: A connection to a database or other service was requested using
a connect identifier, and the connect identifier specified could not
be resolved into a connect descriptor using one of the naming methods
configured. For example, if the type of connect identifier used was a
net service name then the net service name could not be found in a
naming method repository, or the repository could not be
located or reached.
