Dropping connected users in Oracle database - oracle

I want to drop some users in Oracle DB using sqlplus but I am getting error:
SQL> DROP USER test CASCADE;
DROP USER test CASCADE
*
ERROR at line 1:
ORA-01940: cannot drop a user that is currently connected
I followed the link in SO to find out the sessions - Dropping a connected user from an Oracle 10g database schema
But when I ran the command I am not getting any results:
SQL> select sid,serial# from v$session where username = 'test';
no rows selected
Please help me how to drop users in this case.

Users are all capitals in v$session (and data dictionary views). If you match with capitals you should find your session to kill.
SELECT s.sid, s.serial#, s.status, p.spid
FROM v$session s, v$process p
WHERE s.username = 'TEST' --<<<--
AND p.addr(+) = s.paddr
/
Pass actual SID and SERIAL# values for user TEST then drop user...:
ALTER SYSTEM KILL SESSION '<SID>, <SERIAL>'
/

Solution :
login as sysdaba:
sqlplus / as sysdba
then:
sql>Shutdown immediate;
sql>startup restrict;
sql>drop user TEST cascade;
If you want to re-activate DB normally either reset the server or :
sql>Shutdown immediate;
sql>startup;
:)

Issue has been fixed using below procedure :
DECLARE
v_user_exists NUMBER;
user_name CONSTANT varchar2(20) := 'SCOTT';
BEGIN
LOOP
FOR c IN (SELECT s.sid, s.serial# FROM v$session s WHERE upper(s.username) = user_name)
LOOP
EXECUTE IMMEDIATE
'alter system kill session ''' || c.sid || ',' || c.serial# || ''' IMMEDIATE';
END LOOP;
BEGIN
EXECUTE IMMEDIATE 'drop user ' || user_name || ' cascade';
EXCEPTION WHEN OTHERS THEN
IF (SQLCODE = -1940) THEN
NULL;
ELSE
RAISE;
END IF;
END;
BEGIN
SELECT COUNT(*) INTO v_user_exists FROM dba_users WHERE username = user_name;
EXIT WHEN v_user_exists = 0;
END;
END LOOP;
END;
/

Do a query:
SELECT * FROM v$session s;
Find your user and do the next query (with appropriate parameters):
ALTER SYSTEM KILL SESSION '<SID>, <SERIAL>';

If you use RAC then you need to use GV$* views instead V$*.
Try to find your session by
select * from gv$session where username = 'test';
and then you can kill the session by
alter system kill session 'sid, serial#, #inst_id' immediate;

This can be as simple as:
SQL> ALTER SYSTEM ENABLE RESTRICTED SESSION;
SQL> DROP USER test CASCADE;
SQL> ALTER SYSTEM DISABLE RESTRICTED SESSION;

go to services in administrative tools and select oracleserviceSID and restart it

I was trying to follow the flow described here - but haven't luck to completely kill the session.. Then I fond additional step here:
http://wyding.blogspot.com/2013/08/solution-for-ora-01940-cannot-drop-user.html
What I did:
1. select 'alter system kill session ''' || sid || ',' || serial# || ''';' from v$session where username = '<your_schema>'; - as described below.Out put will be something like this:alter system kill session '22,15' immediate;
2. alter system disconnect session '22,15' IMMEDIATE ; - 22-sid, 15-serial - repeat the command for each returned session from previous command
3. Repeat steps 1-2 while select... not return an empty table
4. Call
drop user...
What was missed - call alter system disconnect session '22,15' IMMEDIATE ; for each of session returned by select 'alter system kill session '..

Sometimes Oracle drop user takes long time to execute. In that case user might be connected to the database. Better you can kill user session and drop the user.
SQL> select 'alter system kill session ''' || sid || ',' || serial# || ''' immediate;' from v$session where username ='&USERNAME';
SQL> DROP USER barbie CASCADE;

I had the same problem, Oracle config in default affects letter register. In exact my Scheme_Name was written all Capital letters. You can see your Scheme_Name on "Other Users" tab, if you are using Oracle S

Basically I believe that killing all sessions should be the solution, but...
I found similar discussion - https://community.oracle.com/thread/1054062 to my problem and that was I had no sessions for that users, but I still received the error. I tried also second the best answer:
sql>Shutdown immediate;
sql>startup restrict;
sql>drop user TEST cascade;
What worked for me at the end was to login as the user, drop all tables manually - select for creating drop statements is
select 'drop table ' || TABLE_NAME || ';' from user_tables;
(Needs to be re-run several times because of references)
I have no idea how is that related, I dropped also functions and sequences (because that was all I had in schema)
When I did that and I logged off, I had several sessions in v$session table and when I killed those I was able to drop user.
My DB was still started in restricted mode (not sure if important or not).
Might help someone else.
BTW: my Oracle version is Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production

//'SYS' is username from where you wanted to kill session'
SELECT * FROM DBA_TAB_PRIVS WHERE GRANTEE = 'SYS';
**Step 1:**
CREATE OR REPLACE PROCEDURE sys.kill_session(p_sid NUMBER, p_serial NUMBER)
AS
v_user VARCHAR2(30);
BEGIN
SELECT MAX(username)
INTO v_user
FROM v$session
WHERE sid = p_sid
AND serial# = p_serial;
**Step 2**
create or replace procedure kill_session( p_sid in number, p_serial# in number)
is v_count pls_integer;
BEGIN
select count(*) into v_count
from V$session
where username = 'SYS'
and sid = p_sid
and serial# = p_serial# ;
if ( v_count = 1 )
then
execute immediate '
alter system kill session ''' ||
to_char(p_sid,'999999')||','||
to_char(p_serial#,'999999')||'''';
else
raise_application_error( -20001,
'You do not own session ''' ||
p_sid || ',' || p_serial# ||
'''' );
end if;
END;
/
**Step 3**
grant execute on kill_session to SYS;
**Step 4**
select inst_id, sid, serial#, username, action, program, service_name, con_id from gv$session where username like 'FCM_469';
Check there will be no sessions now
**Step 5**
DROP USER USER_345 CASCADE;
Output:User Dropped

Here's how I "automate" Dropping connected users in Oracle database:
# A shell script to Drop a Database Schema, forcing off any Connected Sessions (for example, before an Import)
# Warning! With great power comes great responsibility.
# It is often advisable to take an Export before Dropping a Schema
if [ "$1" = "" ]
then
echo "Which Schema?"
read schema
else
echo "Are you sure? (y/n)"
read reply
[ ! $reply = y ] && return 1
schema=$1
fi
sqlplus / as sysdba <<EOF
set echo on
alter user $schema account lock;
-- Exterminate all sessions!
begin
for x in ( select sid, serial# from v\$session where username=upper('$schema') )
loop
execute immediate ( 'alter system kill session '''|| x.Sid || ',' || x.Serial# || ''' immediate' );
end loop;
dbms_lock.sleep( seconds => 2 ); -- Prevent ORA-01940: cannot drop a user that is currently connected
end;
/
drop user $schema cascade;
quit
EOF

Related

How to delete sequences and procedures during logoff trigger?

Could you please help me in a unique situation I am in. I am receiving "ORA-30511: invalid DDL operation in system triggers" when dropping sequences and procedures during logoff trigger.
I need to delete tables, sequences and procedures of users before logoff event happens. I am writing the table details in DB_OBJECTS table upon create using a separate trigger. Below is my logoff trigger - could you please help me where I am doing wrong. Dropping tables is working fine in the below code. Only Dropping sequences and procedures is giving me "ORA-30511: invalid DDL operation in system triggers" error.
CREATE OR REPLACE TRIGGER DELETE_BEFORE_LOGOFF
BEFORE LOGOFF ON DATABASE
DECLARE
USER_ID NUMBER := SYS_CONTEXT('USERENV', 'SESSIONID');
BEGIN
FOR O IN (SELECT USER, OBJECT_NAME, OBJECT_TYPE
FROM DB_OBJECTS WHERE SID = USER_ID
AND USERNAME = USER AND SYSDATE > CREATED_DTTM) LOOP
IF O.OBJECT_TYPE = 'TABLE' THEN
EXECUTE IMMEDIATE 'DROP TABLE ' || O.USER || '.' || O.OBJECT_NAME || ' CASCADE CONSTRAINTS';
ELSIF O.OBJECT_TYPE = 'SEQUENCE' THEN
EXECUTE IMMEDIATE 'DROP SEQUENCE ' || O.USER || '.' || O.OBJECT_NAME;
ELSIF O.OBJECT_TYPE = 'PROCEDURE' THEN
EXECUTE IMMEDIATE 'DROP PROCEDURE ' || O.USER || '.' || O.OBJECT_NAME;
END IF;
END LOOP;
EXCEPTION WHEN NO_DATA_FOUND THEN NULL;
END;
/
That's a simple one.
Error code: ORA-30511
Description: invalid DDL operation in system triggers
Cause: An attempt was made to perform an invalid DDL operation in a system trigger. Most DDL operations currently are not supported in system triggers. The only currently supported DDL operations are table operations and ALTER/COMPILE operations.
Action: Remove invalid DDL operations in system triggers.
That's why only
Dropping tables is working fine
succeeded.
Therefore, you can't do that using trigger.
You asked (in a comment) how to drop these objects, then. Manually, as far as I can tell. Though, that's quite unusual - what if someone accidentally logs off? You'd drop everything they created. If you use that schema for educational purposes (for example, every student gets their own schema), then you could create a "clean-up" script you'd run once class is over. Something like this:
SET SERVEROUTPUT ON;
DECLARE
l_user VARCHAR2 (30) := 'SCOTT';
l_str VARCHAR2 (200);
BEGIN
IF USER = l_user
THEN
FOR cur_r IN (SELECT object_name, object_type
FROM user_objects
WHERE object_name NOT IN ('EMP',
'DEPT',
'BONUS',
'SALGRADE'))
LOOP
BEGIN
l_str :=
'drop '
|| cur_r.object_type
|| ' "'
|| cur_r.object_name
|| '"';
DBMS_OUTPUT.put_line (l_str);
EXECUTE IMMEDIATE l_str;
EXCEPTION
WHEN OTHERS
THEN
NULL;
END;
END LOOP;
END IF;
END;
/
PURGE RECYCLEBIN;
It is far from being perfect; I use it to clean up my Scott schema I use to answer questions on various sites so - once it becomes a mess, I run that PL/SQL code several times (because of possible foreign key constraint).
Other option is to keep a create user script(s) (along with all grant statements) and - once class is over - drop existing user and simply recreate it.
Or, if that user contains some pre-built tables, keep export file (I mean, result of data pump export) and import it after the user is dropped.
There are various options - I don't know whether I managed to guess correctly, but now you have something to think about.

Oracle logoff trigger to get sql's executed by session

I have created a table which contains the host names of all the trusted sources. I have written a oracle log off trigger to fetch details of all the sql executed by that session if the connection's host is not amongst the snif_session table. I am taking the output to a utl_file output which contains the sid, hostname, time connected.
SQL> select * from snif_Session;
ALLOWED_HOST
--------------------------------------------------
RND1
WORKGROUP\RND1
The place where i am getting stuck is what query to use to get all the sql's executed by that particular session ( i can get the sid from v$mystat).
does this work best :
select a.sql_id
,b.sql_text
from dba_hist_active_sess_history a
,dba_hist_sqltext b
where a.sql_id=b.sql_id
or
select s.sid
, s.serial#
, a.sql_text
from v$session s
join v$sqlarea a
on a.hash_value = s.sql_hash_value ;
This is the code i have written (block) which i will be placing inside a trigger.
declare
machine_id varchar2(50);
val int;
auth_terminal varchar2(50);
check_machine varchar2(1000);
mydate char(50);
osuser_1 varchar2(50);
sid_1 int;
sql_query_1 varchar2(5000);
machine_1 varchar2(50);
trace_info UTL_FILE.FILE_TYPE;
begin
select machine into check_machine
from v$session
where sid in (select distinct(sid) from v$mystat) ;
select count(*) into val
from snif_session
where allowed_host=check_machine;
if ( 1=val) then
dbms_output.put_line(check_machine|| ' dont check host' );
else
dbms_output.put_line(check_machine || ' check host' );
end if;
select osuser,sid,machine
into osuser_1,sid_1,machine_1
from v$session
where sid in (select distinct(sid) from v$mystat);
SELECT TO_char(systimestamp,'mm/dd/yyyy HH24:MI:SS') into mydate
FROM DUAL;
dbms_output.put_line(mydate || sid_1 || ' ' || osuser_1 || ' '|| machine_1);
trace_info := UTL_FILE.FOPEN('UTL_DIR', 'trace_info_file.txt', 'W');
UTL_FILE.PUTF(trace_info,mydate||' '||sid_1||' '||osuser_1||' '|| machine_1);
UTL_FILE.FCLOSE(trace_info);
EXCEPTION
WHEN utl_file.invalid_path THEN
raise_application_error(-20000, 'ERROR: Invalid PATH FOR file.');
end;
I need to include the 'sql queries' also executed by session in the utl_file output.
"I need to include the 'sql queries' also executed by session"
Neither of your suggested queries will give you all the SQL executed by a session.
V$SESSION is a dynamic view, so it just shows what is happening in a session right now.
DBA_HIST_ACTIVE_SESS_HISTORY is a series of snapshots of running SQL. It is intended for performance profiling, and as such it is basically a random sub-set of active statements. Also, it is part of the Diagnostics and Tuning Pack: you will be in breach of your license if you use it without paying the additional charge.
It appears that what you really need is an audit trail. Instead of rolling your own, why not investigate the functionality Oracle already has? There's AUDIT to track DDL activity. There's Fine-grained Auditing to monitor lower-level DML. Find out more.

ALTER SYSTEM is not executing in jruby

I am trying to execute plsql block in which I have ALTER USER and then ALTER SYSTEM statements one after other. ALTER USER is executing but ALTER SYSTEM is not.
My code does the following:
1. Connects to the database using jdbc driver.
2. Changes the login user of a particular user (here I am using ALTER USER statement).
3. Kills the session of that particular user before dropping it (here I use ALTER SYSTEM statement which is not running).
Below is the code fragment which is not running for me.
users = ['ABC', 'XYZ']
$users.each do|x|
if( is_usr?("#{x}") )
puts "Working on #{x}"
stmt = <<-EOF
DECLARE
id NUMber(10);
s_num NUMBER(10);
CURSOR cur IS
SELECT sid, serial#
FROM v$session WHERE username like ('#{x}');
BEGIN
OPEN cur;
LOOP
FETCH cur INTO id, s_num;
dbms_output.put_line(id||' '||s_num);
EXECUTE IMMEDIATE 'ALTER USER #{x} IDENTIFIED BY dummypass';
EXECUTE IMMEDIATE 'ALTER SYSTEM KILL SESSION ''' ||id|| ',' ||s_num||'''';
EXIT when sess_cur%notfound;
END LOOP;
CLOSE cur;
END;
EOF
puts "#{stmt}"
plsql = #conn.create_statement
plsql.execute_update(stmt)
else
puts "#{x} does not exist"
end
end
Output looks like this:
Working on ABC
DECLARE
id NUMber(10);
s_num NUMBER(10);
CURSOR cur IS
SELECT sid, serial#
FROM v$session WHERE username like ('ABC');
BEGIN
OPEN cur;
LOOP
FETCH cur INTO id, s_num;
dbms_output.put_line(id||' '||s_num);
EXECUTE IMMEDIATE 'ALTER USER ABC IDENTIFIED BY dummypass';
EXECUTE IMMEDIATE 'ALTER SYSTEM KILL SESSION ''' ||id|| ',' ||s_num||'''';
EXIT when sess_cur%notfound;
END LOOP;
CLOSE cur;
END;
Working on XYZ
DECLARE
id NUMber(10);
s_num NUMBER(10);
CURSOR cur IS
SELECT sid, serial#
FROM v$session WHERE username like ('XYZ');
BEGIN
OPEN cur;
LOOP
FETCH cur INTO id, s_num;
dbms_output.put_line(id||' '||s_num);
EXECUTE IMMEDIATE 'ALTER USER XYZ IDENTIFIED BY dummypass';
EXECUTE IMMEDIATE 'ALTER SYSTEM KILL SESSION ''' ||id|| ',' ||s_num||'''';
EXIT when sess_cur%notfound;
END LOOP;
CLOSE cur;
END;
Observation after running this script:
1. I am able to login to db as ABC and XYZ with 'dummypass' as password. Hence I know that ALTER USER statement has been run successfully.
2. I still see all the same session ids and serial#s for 'ABC' and 'XYZ'. Hence I know that ALTER SYSTEM statement did not run.
I am struggling in fixing this one since past 3-days. Please help me in fixing this. Thanks in advance.
ALTER SYSTEM KILL SESSION does not instantly get rid of the session. It only marks it for being killed. Normally a background process will get rid of it in a minute. If there are many uncommitted changes it can take a very long time to rollback everything.
There is no way to speed up the process. The best you can do it ignore those sessions with a predicate like where v$session.status <> 'KILLED'.

change Oracle user account status from EXPIRE(GRACE) to OPEN

After getting the message Your password will be expired with in 7 days, I changed the password expire days of the default profile to UNLIMITED. But the account status of some users are still remaining in EXPIRE(GRACE).
Any way to change the Oracle user account status from EXPIRE(GRACE) to OPEN without resetting the password?
No, you cannot directly change an account status from EXPIRE(GRACE) to OPEN without resetting the password.
The documentation says:
If you cause a database user's password to expire with PASSWORD
EXPIRE, then the user (or the DBA) must change the password before
attempting to log into the database following the expiration.
However, you can indirectly change the status to OPEN by resetting the user's password hash to the existing value. Unfortunately, setting the password hash to itself has the following complications, and almost every other solution misses at least one of these issues:
Different versions of Oracle use different types of hashes.
The user's profile may prevent re-using passwords.
Profile limits can be changed, but we have to change the values back at the end.
Profile values are not trivial because if the value is DEFAULT, that is a pointer to the DEFAULT profile's value. We may need to recursively check the profile.
The following, ridiculously large PL/SQL block, should handle all of those cases. It should reset any account to OPEN, with the same password hash, regardless of Oracle version or profile settings. And the profile will be changed back to the original limits.
--Purpose: Change a user from EXPIRED to OPEN by setting a user's password to the same value.
--This PL/SQL block requires elevated privileges and should be run as SYS.
--This task is difficult because we need to temporarily change profiles to avoid
-- errors like "ORA-28007: the password cannot be reused".
--
--How to use: Run as SYS in SQL*Plus and enter the username when prompted.
-- If using another IDE, manually replace the variable two lines below.
declare
v_username varchar2(128) := trim(upper('&USERNAME'));
--Do not change anything below this line.
v_profile varchar2(128);
v_old_password_reuse_time varchar2(128);
v_uses_default_for_time varchar2(3);
v_old_password_reuse_max varchar2(128);
v_uses_default_for_max varchar2(3);
v_alter_user_sql varchar2(4000);
begin
--Get user's profile information.
--(This is tricky because there could be an indirection to the DEFAULT profile.
select
profile,
case when user_password_reuse_time = 'DEFAULT' then default_password_reuse_time else user_password_reuse_time end password_reuse_time,
case when user_password_reuse_time = 'DEFAULT' then 'Yes' else 'No' end uses_default_for_time,
case when user_password_reuse_max = 'DEFAULT' then default_password_reuse_max else user_password_reuse_max end password_reuse_max,
case when user_password_reuse_max = 'DEFAULT' then 'Yes' else 'No' end uses_default_for_max
into v_profile, v_old_password_reuse_time, v_uses_default_for_time, v_old_password_reuse_max, v_uses_default_for_max
from
(
--User's profile information.
select
dba_profiles.profile,
max(case when resource_name = 'PASSWORD_REUSE_TIME' then limit else null end) user_password_reuse_time,
max(case when resource_name = 'PASSWORD_REUSE_MAX' then limit else null end) user_password_reuse_max
from dba_profiles
join dba_users
on dba_profiles.profile = dba_users.profile
where username = v_username
group by dba_profiles.profile
) users_profile
cross join
(
--Default profile information.
select
max(case when resource_name = 'PASSWORD_REUSE_TIME' then limit else null end) default_password_reuse_time,
max(case when resource_name = 'PASSWORD_REUSE_MAX' then limit else null end) default_password_reuse_max
from dba_profiles
where profile = 'DEFAULT'
) default_profile;
--Get user's password information.
select
'alter user '||name||' identified by values '''||
spare4 || case when password is not null then ';' else null end || password ||
''''
into v_alter_user_sql
from sys.user$
where name = v_username;
--Change profile limits, if necessary.
if v_old_password_reuse_time <> 'UNLIMITED' then
execute immediate 'alter profile '||v_profile||' limit password_reuse_time unlimited';
end if;
if v_old_password_reuse_max <> 'UNLIMITED' then
execute immediate 'alter profile '||v_profile||' limit password_reuse_max unlimited';
end if;
--Change the user's password.
execute immediate v_alter_user_sql;
--Change the profile limits back, if necessary.
if v_old_password_reuse_time <> 'UNLIMITED' then
if v_uses_default_for_time = 'Yes' then
execute immediate 'alter profile '||v_profile||' limit password_reuse_time default';
else
execute immediate 'alter profile '||v_profile||' limit password_reuse_time '||v_old_password_reuse_time;
end if;
end if;
if v_old_password_reuse_max <> 'UNLIMITED' then
if v_uses_default_for_max = 'Yes' then
execute immediate 'alter profile '||v_profile||' limit password_reuse_max default';
else
execute immediate 'alter profile '||v_profile||' limit password_reuse_max '||v_old_password_reuse_max;
end if;
end if;
end;
/
Compilation from jonearles' answer, http://kishantha.blogspot.com/2010/03/oracle-enterprise-manager-console.html and http://blog.flimatech.com/2011/07/17/changing-oracle-password-in-11g-using-alter-user-identified-by-values/ (Oracle 11g):
To stop this happening in the future do the following.
Login to sqlplus as sysdba -> sqlplus "/as sysdba"
Execute ->ALTER PROFILE DEFAULT LIMIT FAILED_LOGIN_ATTEMPTS UNLIMITED PASSWORD_LIFE_TIME UNLIMITED;
To reset users' status, run the query:
select
'alter user ' || su.name || ' identified by values'
|| ' ''' || spare4 || ';' || su.password || ''';'
from sys.user$ su
join dba_users du on ACCOUNT_STATUS like 'EXPIRED%' and su.name = du.username;
and execute some or all of the result set.
set long 9999999
set lin 400
select DBMS_METADATA.GET_DDL('USER','YOUR_USER_NAME') from dual;
This will output something like this:
SQL> select DBMS_METADATA.GET_DDL('USER','WILIAM') from dual;
DBMS_METADATA.GET_DDL('USER','WILIAM')
--------------------------------------------------------------------------------
CREATE USER "WILIAM" IDENTIFIED BY VALUES 'S:6680C1468F5F3B36B726CE7620F
FD9657F0E0E49AE56AAACE847BA368CEB;120F24A4C2554B4F'
DEFAULT TABLESPACE "USER"
TEMPORARY TABLESPACE "TEMP"
PASSWORD EXPIRE
Just use the first piece of that with alter user instead:
ALTER USER "WILIAM" IDENTIFIED BY VALUES 'S:6680C1468F5F3B36B726CE7620F
FD9657F0E0E49AE56AAACE847BA368CEB;120F24A4C2554B4F';
This will put the account back in to OPEN status without changing the password (as long as you cut and paste correctly the hash value from the output of DBMS_METADATA.GET_DDL) and you don't even need to know what the password is.
In case you know the password of that user, or you would like to guess it, do the following:
connect user/password
If this command connects successufully, you will see the message "connected", otherwise you'd see an error message. If you are then successufull logging, that means that you know the password.
In that case, just do:
alter user NAME_OF_THE_USER identified by OLD_PASSWORD;
and this will reset the password to the same password as before and also reset the account_status for that user.
Step-1 Need to find user details by using below query
SQL> select username, account_status from dba_users where username='BOB';
USERNAME ACCOUNT_STATUS
------------------------------ --------------------------------
BOB EXPIRED
Step-2 Get users password by using below query.
SQL>SELECT 'ALTER USER '|| name ||' IDENTIFIED BY VALUES '''|| spare4 ||';'|| password ||''';' FROM sys.user$ WHERE name='BOB';
ALTER USER BOB IDENTIFIED BY VALUES 'S:9BDD17811E21EFEDFB1403AAB1DD86AB481E;T:602E36430C0D8DF7E1E453;2F9933095143F432';
Step -3 Run Above alter query
SQL> ALTER USER BOB IDENTIFIED BY VALUES 'S:9BDD17811E21EFEDFB1403AAB1DD86AB481E;T:602E36430C0D8DF7E1E453;2F9933095143F432';
User altered.
Step-4 :Check users account status
SQL> select username, account_status from dba_users where username='BOB';
USERNAME ACCOUNT_STATUS
------------------------------ --------------------------------
BOB OPEN
PART I (FIND IF USER EXISTS)
--could check with a system type account e.g.SYS
SQL> select username, account_status from dba_users where username='BOB';
SQL> select username, account_status from dba_users where username like 'BOB%';
SQL> select username, account_status from dba_users where like '%BOB%';
PART II Changing the account properties
SQL> ALTER user [username] account UNLOCK; --unlocks the account it it was locked
SQL> Alter user [username] IDENTIFIED BY "password"; --would change the password for user
SQL> ALTER user [username] account UNLOCK; --unlocks the account it it was locked
SQL> Alter user [username] IDENTIFIED BY "password"; --would change the password for user
This one is working for me.

Dropping Oracle connections using a query

I wanted to drop/kill connections made to specific schema of a database. Could you please sugest a prudent way to do this?
Cheers
In order to prevent a user from connecting you could lock the account:
ALTER USER usr ACCOUNT LOCK;
If you want to disconnect all sessions of a user, you could use the method described in another SO:
BEGIN
FOR x IN (SELECT Sid, Serial# FROM v$session WHERE username = 'USR') LOOP
EXECUTE IMMEDIATE 'Alter System Kill Session ''' || x.Sid || ','
|| x.Serial# || ''' IMMEDIATE';
END LOOP;
END;

Resources