How to analyze a specific partition only using dbms_stats

To analyze only specific partitions, including subpartitions, use the dbms_stats.gather_table_stats while specifying the directives PART_NAME and GRANULARITY.

The following query reveals that several of the recently added subpartitions in the COMPLETED_ORDERS partition have not yet been analyzed:

SELECT P.PARTITION_NAME "partition name",P.NUM_ROWS "partition rows",P.LAST_ANALYZED "last analyzed", SP.SUBPARTITION_NAME "subpart name", SP.NUM_ROWS "subpartition rows",SP.LAST_ANALYZED "subpart last analyzed"
FROM DBA_TAB_PARTITIONS P INNER JOIN DBA_TAB_SUBPARTITIONS SP
ON (P.TABLE_NAME = SP.TABLE_NAME)
WHERE P.TABLE_NAME='ORDERS'
AND P.PARTITION_NAME = SP.PARTITION_NAME
AND P.PARTITION_NAME = 'COMPLETED_ORDERS'
AND SP.NUM_ROWS IS NULL
ORDER BY P.PARTITION_NAME DESC,SP.SUBPARTITION_NAME;

Output:

partition name	partition rows	last analyzed	subpart name	subpartition rows	subpart last analyzed
COMPLETED_ORDERS	2527257	19/10/2015 07:17:44	CO_SP_2017
COMPLETED_ORDERS	2527257	19/10/2015 07:17:44	CO_SP_2018
COMPLETED_ORDERS	2527257	19/10/2015 07:17:44	CO_SP_2019
COMPLETED_ORDERS	2527257	19/10/2015 07:17:44	CO_SP_2020

To analyze them, use dbms_stats with the PART_NAME directive, and the GRANULARITY directive set to "SUBPARTITION"

BEGIN
  SYS.DBMS_STATS.GATHER_TABLE_STATS (
     OwnName        => 'SCOTT'
    ,TabName        => 'ORDERS'
    ,partname       => 'COMPLETED_ORDERS'
    ,Estimate_Percent  => DBMS_STATS.AUTO_SAMPLE_SIZE
    ,method_opt        => 'FOR ALL COLUMNS SIZE AUTO'
    ,Degree            => DBMS_STATS.AUTO_DEGREE
    ,Cascade           => DBMS_STATS.AUTO_CASCADE
    ,granularity       => 'SUBPARTITION'
    ,No_Invalidate     => DBMS_STATS.AUTO_INVALIDATE);
END;
/

After statistics gathering, execute the query again, but without the "AND SP.NUM_ROWS IS NULL" predicative:

partition name	partition rows	last analyzed	subpart name	subpartition rows	subpart last analyzed
COMPLETED_ORDERS	2527257	19/10/2015 07:17:44	CO_SP_2017	0	27/12/2016 09:10:04
COMPLETED_ORDERS	2527257	19/10/2015 07:17:44	CO_SP_2018	0	27/12/2016 09:10:05
COMPLETED_ORDERS	2527257	19/10/2015 07:17:44	CO_SP_2019	0	27/12/2016 09:10:07
COMPLETED_ORDERS	2527257	19/10/2015 07:17:44	CO_SP_2020	0	27/12/2016 09:10:08

The 12.2 version of dbms_stats.gather_table_stats is documented here

How to create a partitioned table using a subpartition template

Using templates for your subpartitions is a handy shortcut to avoid specifying attributes for every subpartition in the table.

Oracle calls this concept "vertical striping", since it allows for each subpartition matching the template to end up in the same tablespace and thus allows you to "stripe" your partitions across multiple tablespaces, even though they logically belong to different partitions.

You only describe subpartitions once in the template; Oracle will then apply the template to every partition you create in the table.

The original table's layout is shown below. It is an imaginative tables that will store received documents in a governmental office.
In this example, the documents stored in the CLOB column will be saved in the same tablespace based on year, rather than the type of document it represents.

It will create

* A heap-organized, LIST-LIST partitioned table
* A column of type CLOB (character large object). We will call the CLOB object "REC_DOCS_XML_CLOB"
* 2 pre-defined LIST partitions
* 4 pre-defined LIST sub-partitions
* A subpartition template to simplify future additions of partitions.

CREATE TABLE RECEIVED_DOCUMENTS
(
  UUID                 VARCHAR2(160 BYTE),
  FISCAL_YEAR          NUMBER(4),
  DOCUMENTTYPE         VARCHAR2(100 CHAR),
  DOCUMENTNAME         VARCHAR2(1000 CHAR),
  DOCUMENTSTATE        VARCHAR2(30 CHAR),
  VALID                CHAR(1 BYTE),
  CREATED_TIMESTAMP    NUMBER(20),
  VERSION              NUMBER(20),
  DATA_XML             CLOB,
  FORMAT               VARCHAR2(1000 CHAR),
  PERIOD               VARCHAR2(1000 CHAR)
 )
LOB (DATA_XML) STORE AS SECUREFILE REC_DOCS_XML_CLOB(
 TABLESPACE RECEIVED_DOCUMENTS_LOB_DATA
 COMPRESS HIGH
)
-- The table definition is stored in the tablespace DOCS_DATA
TABLESPACE DOCS_DATA
PARTITION BY LIST (DOCUMENTTYPE)
SUBPARTITION BY LIST (PERIOD)
SUBPARTITION TEMPLATE
  (SUBPARTITION SP_2014 VALUES ('2014') TABLESPACE DOCS_2014,
   SUBPARTITION SP_2015 VALUES ('2015') TABLESPACE DOCS_2015,
   SUBPARTITION SP_2016 VALUES ('2016') TABLESPACE DOCS_2016,
   SUBPARTITION SP_DEFAULT VALUES (default) TABLESPACE DOCS_DATA
   )
(
  PARTITION SETTELM
    VALUES ('SETTLEM_ACCEPTED', 'SETTLEM_REJECTED'),
  PARTITION APPLICATIONS
    VALUES ('SINGLE_PARENT_SUPP','UNEMPLOYMENT_SUPP','CHILD_SUPP','HOUSING_SUPP')    
)
;

If you later would like to add a partition, it is as simple as

ALTER TABLE RECEIVED_DOCUMENTS
 ADD PARTITION APPLICANT VALUES ('FAMILY','SINGLE_PARENT','ASYLUM_SEEKER')
;

Similarly, dropping a partition with its subpartition would be done with:

ALTER TABLE RECEIVED_DOCUMENTS
DROP PARTITION APPLICATION;

Notice that if you have a default partition to handle incoming data that doesn't fit in any particular partition, you will get an error when attempting to add a partition.

Sources:

"Specifying Subpartition Templates to Describe Composite Partitioned Tables"

"Specifying a Subpartition Template for a *-List Partitioned Table"

How to remove the APEX option from the database

cd $ORACLE_HOME/apex
sqlplus / as sysdba
@apxremov.sql
drop public synonym htmldb_system;
drop PACKAGE HTMLDB_SYSTEM;

If you have older APEX installations, they may be left in the database, but not registred in the dba_registry.

I had an old APEX schema called APEX_030200, with several invalid objects:

OWNER	OBJECT_TYPE	COUNT(*)
PUBLIC	SYNONYM	3
APEX_030200	PACKAGE	2
APEX_030200	PACKAGE BODY	114
APEX_030200	PROCEDURE	3

This means that the script above won't work. You will get this output when attempting to remove the installation:

sqlplus / as sysdba @apxremov.sql
...
Error:
You can only use this script to remove Application Express

I found some useful information about these situations at this blog

Basically, you can simply drop the old schema directly.

Check first:

SELECT username, 'drop user ' || username || ' cascade;' AS remove_statement
  FROM dba_users
 WHERE     (username LIKE 'FLOWS_%' OR username LIKE 'APEX_%')
       AND username NOT IN ('FLOWS_FILES',
                            'APEX_PUBLIC_USER',
                            'APEX_LISTENER',
                            'APEX_REST_PUBLIC_USER',
                            'APEX_INSTANCE_ADMIN_USER')
       AND username NOT IN (SELECT schema s
                              FROM dba_registry
                             WHERE comp_id = 'APEX');

So cleaning up can be done as easily as this:

drop user APEX_030200 cascade;

Will interrupting a "split partition"-command cause any harm to your database?

Will interrupting a "alter table split partition"-command cause any harm to your database?

No, it will not. It is safe to kill the session. Oracle will be able to recover and the table would be left in its original state, prior to time when the "alter table split partition" command was executed.

I was recently in contact with Oracle support regarding such a case. My goal was to split a sub-partition, in order to accommodate rows for years 2017 to 2020, but there was way too much concurrent activities in the database to complete the "alter table split partition"-command.
The database was almost completely non-responsive and there was pressure to finish within a certain time frame.

The supporting engineer confirmed that there would be some rollback activities in the wake of this command, how much depended on the activity level in the database during the time when the DDL was executing.

He added the following explanation to how Oracle handles the split internally:

As for kill the split partition, the way it works internally is to create temporary segments for the 2 new partitions it is splitting into, and when the operation is complete, these new temporary segments are attached to the original table and become the new partitions. So the result of this is that it's perfectly safe to terminate the split partition, and it simply stops its work, drops the temporary segments, and you are left with the original table in-tact, so there will be no ill-effects of this.

How to create a common and a local user in a 12c multitenant database

In a multitenant container database, there are two types of users:

* Common users, who are known in both the root containers and in all the pluggable database containers
* Local users, who are only known in a single pluggable database container

Common users can, if granted the necessary privileges, perform administrative tasks across all the PDBs in multitenant database.
They can also perform tasks specific to the container database, also called the ROOT container.

To create a common user, make sure you are connected to the ROOT container

On my client, my tnsnames.ora entry looks as follows:

# container database
CDB =
   (DESCRIPTION =
     (ADDRESS = (PROTOCOL = TCP)(HOST = myhost.mydomain.no)(PORT = 1531))
     (CONNECT_DATA =
       (SERVER = DEDICATED)
       (SERVICE_NAME = "container#db01")
     )
   )

Since my client is a windows pc, I start sqlplus from the start menu, and connect as system@cdb and enter the password.
My default container will be CDB$ROOT, which is what you need to create a common user:

show con_name

CON_NAME
------------------------------
CDB$ROOT

Create the common user:

create user C##DBAMASTER
identified by ****
default tablespace USERS
temporary tablespace TEMP
quota unlimited on USERS
container=all;

SQL> user C##DBAMASTER created.

Note the new rules for creating common users in a CDB database:
In Oracle Database 12c Release 1 (12.1.0.1), the name of a common user must begin with C## or c##

Verify that the common user was created:

select USERNAME,CREATED,LAST_LOGIN,COMMON
from dba_USERS
where trunc(created) = trunc(sysdate)

USERNAME             CREATED   LAST_LOGIN                               COM
-------------------- --------- ---------------------------------------- ---
C##DBAMASTER         18-DEC-16 18-DEC-16 03.16.16.000000000 PM +01:00   YES

Give the common user the right to create a session, to switch between all containers in the CDB and the right to create and drop users in all the containers in the CDB:

grant connect to C##DBAMASTER;
grant set container to C##DBAMASTER container=all;
grant create user to C##DBAMASTER container=all;
grant drop user to C##DBAMASTER container=all;

SQL> Grant succeeded.

Connect to ROOT container as the new common user:

connect C##DBAMASTER/***@cdb
Connected.
show user
USER is "C##DBAMASTER"

Switch container:

alter session set container=vpdb01;

SQL> Session altered.

Create a new local user in the current container:

create user "1Z0061"
identified by ****
default tablespace users
quota unlimited on users
temporary tablespace TEMP
container=current;

SQL> User created.

Note that without the "container=all" privilege, the new common user C##DBAMASTER cannot connect directly to the vpdb01 pluggable database

Here is what happened:

SQL> connect C##DBAMASTER/****@vpdb01
ERROR:
ORA-01045: user C##DBAMASTER lacks CREATE SESSION privilege; logon denied


Warning: You are no longer connected to ORACLE.
SQL> connect system/*****@vpdb01
Connected.
SQL> show con_name

CON_NAME
------------------------------
VPDB01
SQL> grant create session to C##DBAMASTER container=current;

Grant succeeded.

SQL> connect C##DBAMASTER/****@vpdb01
Connected.
SQL> show con_name

CON_NAME
------------------------------
VPDB01

This means that these two privileges are distinctly different:

grant create session to C##DBAADMIN container=all;

vs

grant set container to C#DBAADMIN container=all;

How to display the current container in an Oracle multitenant database

You can display the current container your session is currently connected to using three different methods.

First, connect to either the container database or one of the pluggable databases running out of your container database. In this example, I chose to connect to the CDB.


1. Display the current container using the "show con_name" or "show con_id" in sqlplus

SQL> show con_name

CON_NAME
------------------------------
CDB$ROOT --> We are connectted to the ROOT container.

Switch to a different container, and try again:

SQL> alter session set container=vpdb01;

Session altered.

SQL> show con_name

CON_NAME
------------------------------
VPDB01 --> We are now connected to the container named VPDB01.


SQL> show con_id

CON_ID
------------------------------
6 --> The current container id is 6.

2. Display the current container using the SYS_CONTEXT function

In the example below I have thrown in a couple of other useful parameters, along with the
"con_name" and the "con_id" parameters:

select SYS_CONTEXT('userenv','con_name') "container name",
        SYS_CONTEXT('userenv','con_id') "container id",
        SYS_CONTEXT('userenv','CURRENT_SCHEMA') "Current schema",
        SYS_CONTEXT('userenv','SID') "SID"
FROM DUAL;

container name       container id         Current schema       SID
-------------------- -------------------- -------------------- --------
VPDB01               6                    SYSTEM               63

From the output above, we see that we are connected to the container name VPDB01 with con_id 6.

Switch to the root container again, and verify that we are now connected to the ROOT container:

SQL> alter session set container=CDB$ROOT;

Session altered.

Rerun the SYS_CONTEXT statement:

select SYS_CONTEXT('userenv','con_name') "container name",
        SYS_CONTEXT('userenv','con_id') "container id",
        SYS_CONTEXT('userenv','CURRENT_SCHEMA') "Current schema",
        SYS_CONTEXT('userenv','SID') "SID"
FROM DUAL;

container name       container id         Current schema       SID
-------------------- -------------------- -------------------- --------
CDB$ROOT             1                    SYSTEM               63

3. Display the current container using V$CONTAINERS view

This final method only makes sense if you are connected to a non-root container.

SQL> alter session set container=vpdb01;

Session altered.

The result:

SQL> select CON_ID,DBID,name,OPEN_MODE
  2  from v$containers order by con_id;

    CON_ID       DBID NAME                           OPEN_MODE
---------- ---------- ------------------------------ ----------
         6 2049231443 VPDB01                         READ WRITE

If you are connected to the root container, and when querying the v$container, the resulting output will list all containers in your cdb:

SQL> select CON_ID,DBID,name,OPEN_MODE
  2  from v$containers order by con_id;

    CON_ID       DBID NAME                           OPEN_MODE
---------- ---------- ------------------------------ ----------
         1 2294367729 CDB$ROOT                       READ WRITE
         2 3254699093 PDB$SEED                       READ ONLY
         6 2049231443 VPDB01                         READ WRITE

3 rows selected.

I have also written a short blog post about the same topic here, but with a slightly different angle.

How to change passwords for eBS schemas in an Oracle database

In an Oracle database supporting eBS, there are a number of schemas that supports the different modules in eBS. Everything is installed and must be maintained, regardless if the module is in use or not.
If you want to change the passwords for these accounts, you need to do that through the utility AFPASSWD or the deprecated FNDCPASS utility.

Requirements:

* The environment variable TWO_TASK must be set on the eBS application server
* The SYSTEM password for your eBS database
* The current APPS password

I strongly recommend using the same password for all eBS schemas.
Unfortunately, you cannot use special characters in the passwords, so you need to compensate this by making them at least 12-20 characters lang.

To change the passwords, use the following procedure:

1. logon to your eBS application server
2. change user to the owner of the software installation
3. shut down all eBS processes
4. take backup of FND_USER and FND_ORACLE_USERID tables (you can use CTAS for this)

connect apps/oldpassword
create table FND_USER_BUP AS SELECT * FROM FND_USER;
create table FND_ORACLE_USERID_BUP AS SELECT * FROM FND_ORACLE_USERID;

5.

cd $FND_TOP/bin

6. Change the password for all type 3 passwords (meaning all eBS schemas except APPS, APPLSYS,APPLSYSPUB)

./AFPASSWD -c APPS@$TWO_TASK -a

7. Change the passwords for type 2 schema password

./AFPASSWD -c APPS@$TWO_TASK -s APPS

8. Change the password for type 2 schema password APPLSYS

./AFPASSWD -c APPS@$TWO_TASK -s APPLSYS 

9. Change the password for type 2 schema password for APPLSYSPUB. Note that the APPLSYSPUB password must be uppercase, even if you have enabled case sensitive passwords

./AFPASSWD -c APPS@$TWO_TASK -o APPLSYSPUB

10. Update the s_gwyuid_pass variable in the AutoConfig context file to reflect the new password

vi $CONTEXT_FILE

Change from

<oa_user type="GWYUID">
            <username oa_var="s_gwyuid_user">APPLSYSPUB</username>
            <password oa_var="s_gwyuid_pass">PUB</password>
         </oa_user>

to

<oa_user type="GWYUID">
            <username oa_var="s_gwyuid_user">APPLSYSPUB</username>
            <password oa_var="s_gwyuid_pass">YOURNEWSECRETCOMPLICATEDPASSWORD</password>
         </oa_user>

11. verify that the users now have a new password:

sqlplus /nolog
SQL> connect APPS/YOURNEWSECRETCOMPLICATEDPASSWORD
Connected.
SQL> show user
USER is "APPS"

12. start your eBS application processes

Here is a query that will extract the description of each schema, and when the password was last changed:

SELECT ORACLE_USERNAME,LAST_UPDATE_DATE, DESCRIPTION
FROM FND_ORACLE_USERID
WHERE ORACLE_USERNAME IN ('APPS','APPLSYSPUB','APPLSYS','AR','GMO','PFT')
ORDER BY LAST_UPDATE_DATE;

Output:

ORACLE_USERNAME	LAST_UPDATE_DATE	DESCRIPTION
AR	15.12.2016 16:28:45	Oracle Receivables Account
GMO	15.12.2016 16:28:47	Oracle Manufacturing Execution System for Process Manufacturing Account
PFT	15.12.2016 16:28:47	Oracle Profitability Manager Account
APPLSYS	15.12.2016 16:30:34	Application Object Library Account
APPS	15.12.2016 16:30:34	APPS #1 Account
APPLSYSPUB	15.12.2016 16:31:09	Application Object Library Public Account

For a complete list, leave out the WHERE-clause.

Cloning a pluggable database in 12c

I have created a CDB using Oracles database configuration assistant (dbca).
While installing, I choosed to create a Pluggable database, too, called pdbvegdb01.

If you want to make a clone of a PDB, it's a relative simple process.


1. Check your current setup by connecting to the root container (CDB$ROOT), and issue the following query:

select C.PDB_ID,C.PDB_NAME,C.STATUS,C.CON_ID "container id", P.OPEN_MODE,P.restricted
from CDB_PDBS C inner join V$PDBS P
on C.CON_ID = P.CON_ID
order by c.con_id;

PDB_ID	PDB_NAME	STATUS	container id	OPEN_MODE	RESTRICTED
2	PDB$SEED	NORMAL	2	READ ONLY	NO
3	PDBVEGDB01	NORMAL	3	READ WRITE	NO

I would like to clone the PDBVEGDB01, to a new one, that I will name vpdb01.

2. Check if the root container uses OMF (Oracle Managed Files)

select name,value,DESCRIPTION 
from V$SYSTEM_PARAMETER 
WHERE NAME in( 'db_create_file_dest');

NAME	VALUE	DESCRIPTION
db_create_file_dest	/u02/oradata	default database location

It does, and that means your new PDB will inherit this setting.

In this example, I would NOT like Oracle to manage the files in my PDB.
I want to place them in a folder called /u02/oradata/VPDB01.

3. Make directory on server:

mkdir -p /u02/oradata/VPDB01

4. Check the names and paths of the files being used by the source PDB:

select FILE_NAME from CDB_DATA_FILES where CON_ID=3
union
select file_name from cdb_temp_files where con_id=3;

The result of this union is:

FILE_NAME
/u02/oradata/CONTAINER#DB01/436546A3F70642C3E0537800A8C03C16/datafile/o1_mf_system_d4tytlns_.dbf
/u02/oradata/CONTAINER#DB01/436546A3F70642C3E0537800A8C03C16/datafile/o1_mf_sysaux_d4tytlo2_.dbf
/u02/oradata/CONTAINER#DB01/436546A3F70642C3E0537800A8C03C16/datafile/o1_mf_temp_d4tytlo2_.dbf
/u02/oradata/CONTAINER#DB01/436546A3F70642C3E0537800A8C03C16/datafile/o1_mf_users_d4tyw5y9_.dbf

All the above files must be accounted for in your clone script, when deciding not to continue using OMF.

5. If not already done, switch to the root container:

alter session set container = CDB$ROOT;

6. Close the source pdb, and open it read only:

alter PLUGGABLE database pdbvegdb01 CLOSE;
alter PLUGGABLE database pdbvegdb01 OPEN READ ONLY;

7. Clone the source pdb. Notice that I have matched the source pdb's datafiles, one by one, with a file name of my choosing:

create PLUGGABLE DATABASE VPDB01
from pdbvegdb01
FILE_NAME_CONVERT=(
'/u02/oradata/CONTAINER#DB01/436546A3F70642C3E0537800A8C03C16/datafile/o1_mf_system_d4tytlns_.dbf',
'/u02/oradata/VPDB01/system01.dbf',
'/u02/oradata/CONTAINER#DB01/436546A3F70642C3E0537800A8C03C16/datafile/o1_mf_sysaux_d4tytlo2_.dbf',
'/u02/oradata/VPDB01/sysaux01.dbf',
'/u02/oradata/CONTAINER#DB01/436546A3F70642C3E0537800A8C03C16/datafile/o1_mf_temp_d4tytlo2_.dbf',
'/u02/oradata/VPDB01/temp01.dbf'
'/u02/oradata/CONTAINER#DB01/436546A3F70642C3E0537800A8C03C16/datafile/o1_mf_users_d4tyw5y9_.dbf,
'/u02/oradata/VPDB01/users01.dbf'
);

Your sqlplus session should return "pluggable DATABASE created."

8. Open the source pdb for read/write:

alter pluggable database pdbvegdb01 close;
alter pluggable database pdbvegdb01 open read write;

You now see that your freshly cloned database is in status NEW and is MOUNTED, but not open:

PDB_ID	PDB_NAME	STATUS	container id	OPEN_MODE	RESTRICTED
2	PDB$SEED	NORMAL	2	READ ONLY	NO
3	PDBVEGDB01	NORMAL	3	READ WRITE	NO
6	VPDB01	NEW	6	MOUNTED

9. Open the pdb by switching your session container to the newly cloned pdb

alter session set container=vpdb01;

Just to verify, check the open mode of the container.

select CON_ID,DBID,name,OPEN_MODE 
from v$containers order by con_id;

You should have one row worth of output, since you switched from the root container to the pdb container:

CON_ID	DBID	NAME	OPEN_MODE
6	2049231443	VPDB01	MOUNTED

10. Open the pluggable database:

alter pluggable database vpdb01 open;

For the last step to work, you strictly don't need to switch container, it can be done while you have your session set to the root container as well.
But it demonstrates the ability for the DBA to switch containers and work isolated with them, as though they were separate databases.
Finally, let's switch back to the root container and check the status of our PDB's:

alter session set container = CDB$ROOT;

select C.PDB_ID,C.PDB_NAME,C.STATUS,C.CON_ID "container id", P.OPEN_MODE,P.restricted
from CDB_PDBS C inner join V$PDBS P
on C.CON_ID = P.CON_ID
order by c.con_id;

Result:

PDB_ID	PDB_NAME	STATUS	container id	OPEN_MODE	RESTRICTED
2	PDB$SEED	NORMAL	2	READ ONLY	NO
3	PDBVEGDB01	NORMAL	3	READ WRITE	NO
4	VPDB01	NORMAL	4	READ WRITE	NO

How to create a line-by-line comparison between the parameters used in two different databases

Here is a simple way to create a line-by-line comparison between two databases over a database link.

First make sure there is tns Connectivity between the database you execute the script in, and the remote database.

Then, create a datatabase link:

-- create db link from prod to test
create public database link testdb
connect to system
identified by ****
using 'testdb';

-- make sure that the link works before you proceed:
select host_name from v$instance@testdb;

The following script will spool a text file to your current directory, which can be investigated for differences between the two databases' initialization parameters:

set trimspool on
spool parameter_comparison.lst
set lines 200
col name format a40
col "test value" format a50
col "prod value" format a50
select prod.name,prod.value "prod value",test.value "test value"
from v$system_parameter prod full outer join v$system_parameter@testdb test
on prod.name = test.name;

exit

How to find the last password change a user made

Limit the search to those users who changed their password today:

select name,ctime "created", ptime "passw change time",ltime "last locked", lcount "# failed logins"
 from user$
 where trunc(ptime) = trunc(sysdate)
 order by 3 desc;

Example output:

NAME	created	passw change time	last locked	# failed logins
JIM	25.11.2016 02:25:38	12.12.2016 09:59:25		0
JOHN	25.11.2016 02:25:55	12.12.2016 09:53:19		0
JAMES	25.11.2016 02:25:54	12.12.2016 09:29:50		0

How to find dependencies between views and the tables they're based upon

Use the following Query to list the base tables on which the

select o.object_type,o.owner,o.object_name, CASE WHEN D.REFERENCED_NAME = O.OBJECT_NAME THEN NULL
                                            ELSE D.REFERENCED_NAME || '  --> ' || d.referenced_type 
                                            END "dependency to" 
from dba_objects o join dba_dependencies d
on o.object_name = d.name
where object_name in 
(
'MYVIEW1', 
'MYVIEW2',
) 
and object_type <> 'SYNONYM'
order by object_type desc, "dependency to";

Is it possible to temporarily change the system time on my server, without the Oracle instance complaining?

Yes, it's possible. Oracle doesn't care about the wall-clock time, and will keep the redo log stream intact, regardless of what time the hosting server is set to.

The whole procedure is quite simple:

1. shutdown the database and listener

sqlplus / as sysdba
shutdown immediate
exit
lsnrctl stop

2. as root, change the system time. In my example, I am setting it to 10 days into the future:

Thu Dec 15 12:27:00 CET 2016
  [root@myserver ~]# date
  Thu Dec 15 12:27:01 CET 2016

3. Disable NTP på serveren:

  service ntpd stop

4. Open the instance and the listener

sqlplus / as sysdba
startup
exit
lsnrctl start

5. Verify that the database has picked up the new system time

SQL> select startup_time from v$instance;

STARTUP_TIME
-------------------
15.12.2016 12:28:17

6. Have a look at the archived logs:

select name,sequence#, archived,applied, status, completion_time from v$archived_log;

NAME                                                                      SEQUENCE# ARCHIVED  APPLIED    STA COMPLETION_TIME
------------------------------------------------------------------------- ---------- --------- ---------- --- -------------------
/u04/fra/mydb/archivelog/2016_12_05/o1_mf_1_12538__1480935048084626_.arc  12538 YES       NO         A   05.12.2016 11:50:48
/u04/fra/mydb/archivelog/2016_12_05/o1_mf_1_12539__1480935059227231_.arc  12539 YES       NO         A   05.12.2016 11:50:59

Force a log switch and note the time stamp of the last log:

alter system archive log current;

NAME                                                                      SEQUENCE# ARCHIVED  APPLIED    STA COMPLETION_TIME
------------------------------------------------------------------------- ---------- --------- ---------- --- -------------------
/u04/fra/mydb/archivelog/2016_12_05/o1_mf_1_12538__1480935048084626_.arc  12538 YES       NO         A   05.12.2016 11:50:48
/u04/fra/mydb/archivelog/2016_12_05/o1_mf_1_12539__1480935059227231_.arc  12539 YES       NO         A   05.12.2016 11:50:59
/u04/fra/mydb/archivelog/2016_12_15/o1_mf_1_12540__1481801585872720_.arc  12540 YES       NO         A   15.12.2016 12:33:06 

Change back again:

7. shutdown the database and the listener

sqlplus / as sysdba
shutdown immediate
exit
lsnrctl stop

8. enable ntp to have the server syncronized with the current time:

service ntpd start

9. Open the database

sqlplus / as sysdba
startup
exit
lsnrctl start

10. Check the archived logs again. Note that the log sequence doesn't care what the registered time was at the time of the log switch:

select name,sequence#, archived,applied, status, completion_time from v$archived_log;

NAME                                                                      SEQUENCE# ARCHIVED  APPLIED    STA COMPLETION
------------------------------------------------------------------------- ---------- --------- ---------- --- ----------
/u04/fra/mydb/archivelog/2016_12_05/o1_mf_1_12538__1480935048084626_.arc  12538 YES       NO         A   05.12.2016
/u04/fra/mydb/archivelog/2016_12_05/o1_mf_1_12539__1480935059227231_.arc  12539 YES       NO         A   05.12.2016
/u04/fra/mydb/archivelog/2016_12_15/o1_mf_1_12540__1481801585872720_.arc  12540 YES       NO         A   15.12.2016

alter system archive log current;

select name,sequence#, archived,applied, status, completion_time from v$archived_log;

NAME                                                                      SEQUENCE# ARCHIVED  APPLIED    STA COMPLETION
------------------------------------------------------------------------- ---------- --------- ---------- --- ----------
/u04/fra/mydb/archivelog/2016_12_05/o1_mf_1_12538__1480935048084626_.arc  12538 YES       NO         A   05.12.2016
/u04/fra/mydb/archivelog/2016_12_05/o1_mf_1_12539__1480935059227231_.arc  12539 YES       NO         A   05.12.2016
/u04/fra/mydb/archivelog/2016_12_15/o1_mf_1_12540__1481801585872720_.arc  12540 YES       NO         A   15.12.2016 
/u04/fra/mydb/archivelog/2016_12_05/o1_mf_1_12541__1480937880624137_.arc  12541 YES       NO         A   05.12.2016