Quick tip–identity columns

Lets say I’ve been reading about schema separation, and thus I am going to have a schema which owns all of my objects, which I’ll call APP_OWNER, which will have no connection privilege and a separate schema called APP_ADMIN which will take care of all of the DDL tasks.

Here’s my setup:


SQL> create user app_owner identified by app_owner;
 
User created.
 
SQL> grant
  2    create session,
  3    create any table,
  4    create any sequence,
  5  to app_admin identified by app_admin;
 
Grant succeeded.

I have granted APP_ADMIN the ability to create tables in any schema, and create sequences in any schema. I did the latter, because I know that if I use the “IDENTITY” clause for a column, then behind the scenes I’ll be creating a sequence to populate those ascending values.  So it looks like I am ready to go and create my objects.  Let’s create that first table


SQL> conn app_admin/app_admin
Connected.
 
SQL> create table app_owner.t(pk integer generated always as identity);
create table app_owner.t(pk integer generated always as identity)
*
ERROR at line 1:
ORA-01031: insufficient privileges

Hmmm….that is not what we were expecting. It turns out that to create an identity column in another schema you need more than just CREATE ANY SEQUENCE. You also need SELECT ANY SEQUENCE.


SQL> conn / as sysdba
Connected. 
SQL> grant
  2    create session,
  3    create any table,
  4    create any sequence,
  5    select any sequence
  6  to app_admin identified by app_admin;
 
Grant succeeded.
 
SQL> conn app_admin/app_admin
Connected.
 
SQL> create table app_owner.t(pk integer generated always as identity);
 
Table created.

And there we go Smile

Footnote: If you’ve never seen the syntax “grant <privs> to <user> identified by <pass>” it is a quick shortcut to both create the user account and assign privileges in a single command

Transportable Tablespace–part 2

I did a little demo of sharing a tablespace between two databases a few days back – you can see the details here or by just scrolling down Smile if you’re on the home page.

To avoid clouding the demonstration I omitted something in the details, but I’ll share that now, because it could be critical depending on how you currently use transportable tablespaces.

Let me do the most basic of examples now, transporting a tablespace from one database to another:

First, we make our tablespace read only, and Datapump export out the metadata


SQL> alter tablespace DEMO read only;

Tablespace altered.

SQL> exit
Disconnected from Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options

C:\>expdp transport_tablespaces=DEMO directory=TEMP dumpfile=tts.dmp

Export: Release 12.1.0.2.0 - Production on Tue Apr 18 14:16:06 2017

Copyright (c) 1982, 2016, Oracle and/or its affiliates.  All rights reserved.

Username: / as sysdba

Connected to: Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options
Starting "SYS"."SYS_EXPORT_TRANSPORTABLE_01":  /******** AS SYSDBA transport_tablespaces=DEMO directory=TEMP dumpfile=tts.dmp
Processing object type TRANSPORTABLE_EXPORT/PLUGTS_BLK
Processing object type TRANSPORTABLE_EXPORT/TABLE
Processing object type TRANSPORTABLE_EXPORT/TABLE_STATISTICS
Processing object type TRANSPORTABLE_EXPORT/STATISTICS/MARKER
Processing object type TRANSPORTABLE_EXPORT/POST_INSTANCE/PLUGTS_BLK
Master table "SYS"."SYS_EXPORT_TRANSPORTABLE_01" successfully loaded/unloaded
******************************************************************************
Dump file set for SYS.SYS_EXPORT_TRANSPORTABLE_01 is:
  C:\TEMP\TTS.DMP
******************************************************************************
Datafiles required for transportable tablespace DEMO:
  C:\ORACLE\ORADATA\NP12\DEMO.DBF
Job "SYS"."SYS_EXPORT_TRANSPORTABLE_01" successfully completed at Tue Apr 18 14:17:03 2017 elapsed 0 00:00:50

Then, I copy the datafile(s) to the target location and Datapump import the metadata.


C:\>copy C:\oracle\oradata\np12\DEMO.DBF C:\oracle\oradata\db122\DEMO.DBF
        1 file(s) copied.

C:\>impdp transport_datafiles=C:\oracle\oradata\db122\DEMO.DBF directory=TEMP dumpfile=tts.dmp

Import: Release 12.2.0.1.0 - Production on Tue Apr 18 14:17:27 2017

Copyright (c) 1982, 2017, Oracle and/or its affiliates.  All rights reserved.

Username: / as sysdba

Connected to: Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
Master table "SYS"."SYS_IMPORT_TRANSPORTABLE_01" successfully loaded/unloaded
Starting "SYS"."SYS_IMPORT_TRANSPORTABLE_01":  /******** AS SYSDBA transport_datafiles=C:\oracle\oradata\db122\DEMO.DBF directory=TEMP dumpfile=tts.dmp
Processing object type TRANSPORTABLE_EXPORT/PLUGTS_BLK
Processing object type TRANSPORTABLE_EXPORT/TABLE
Processing object type TRANSPORTABLE_EXPORT/TABLE_STATISTICS
Processing object type TRANSPORTABLE_EXPORT/STATISTICS/MARKER
Processing object type TRANSPORTABLE_EXPORT/POST_INSTANCE/PLUGTS_BLK
Job "SYS"."SYS_IMPORT_TRANSPORTABLE_01" successfully completed at Tue Apr 18 14:17:46 2017 elapsed 0 00:00:15

And voila, there is my tablespace in the target database…


C:\>sql122

SQL*Plus: Release 12.2.0.1.0 Production on Tue Apr 18 14:19:08 2017

Copyright (c) 1982, 2016, Oracle.  All rights reserved.

Last Successful login time: Tue Apr 18 2017 14:14:19 +08:00

Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production



SQL> select * from dba_tablespaces
  2  where tablespace_name = 'DEMO'
  3  @pr
==============================
TABLESPACE_NAME               : DEMO
BLOCK_SIZE                    : 8192
INITIAL_EXTENT                : 1048576
NEXT_EXTENT                   : 1048576
MIN_EXTENTS                   : 1
MAX_EXTENTS                   : 2147483645
MAX_SIZE                      : 2147483645
PCT_INCREASE                  : 0
MIN_EXTLEN                    : 1048576
STATUS                        : READ ONLY
CONTENTS                      : PERMANENT
LOGGING                       : LOGGING
FORCE_LOGGING                 : NO
EXTENT_MANAGEMENT             : LOCAL
ALLOCATION_TYPE               : UNIFORM
PLUGGED_IN                    : YES
SEGMENT_SPACE_MANAGEMENT      : AUTO
DEF_TAB_COMPRESSION           : DISABLED
RETENTION                     : NOT APPLY
BIGFILE                       : NO
PREDICATE_EVALUATION          : HOST
ENCRYPTED                     : NO
COMPRESS_FOR                  :
DEF_INMEMORY                  : DISABLED
DEF_INMEMORY_PRIORITY         :
DEF_INMEMORY_DISTRIBUTE       :
DEF_INMEMORY_COMPRESSION      :
DEF_INMEMORY_DUPLICATE        :
SHARED                        : SHARED
DEF_INDEX_COMPRESSION         : DISABLED
INDEX_COMPRESS_FOR            :
DEF_CELLMEMORY                :
DEF_INMEMORY_SERVICE          :
DEF_INMEMORY_SERVICE_NAME     :
LOST_WRITE_PROTECT            : OFF
CHUNK_TABLESPACE              : N

PL/SQL procedure successfully completed.

“Gee thanks, Connor” I can hear you muttering. A demonstration of the flippin’ obvious!

But there is one thing that is not apparent from the export or import logs. Let’s take a squizz at the database alert log for the target, that is, the database we imported the tablespace into.


DW00 started with pid=69, OS id=632, wid=1, job SYS.SYS_IMPORT_TRANSPORTABLE_01
2017-04-18T14:17:34.208631+08:00
Plug in tablespace DEMO with datafile
  'C:\oracle\oradata\db122\DEMO.DBF'
2017-04-18T14:17:46.199645+08:00
ALTER TABLESPACE "DEMO" READ WRITE
Completed: ALTER TABLESPACE "DEMO" READ WRITE
2017-04-18T14:17:46.665512+08:00
ALTER TABLESPACE "DEMO" READ ONLY
Completed: ALTER TABLESPACE "DEMO" READ ONLY

That is a change in 12c. Whilst our imported tablespace ends up as read only as it has always done, during the import process, there was a small window where the tablespace was READ WRITE. This is needed to make some metadata corrections to the tablespace on the way in.

So if you do intend to share tablespaces between databases, that is, share a single copy of the file, make sure take some precautions. On my Windows laptop, standard Windows file locking prohibited me from causing any damage to my source datafile, but on other platforms you might to set those files to read only at the OS level just in case. Of course, you’ll then see a warning during the Datapump import saying that the momentary change to read/write could not be done, but that is not a critical problem.  The transport will still complete.

Sharing a tablespace between 2 databases

I was reading an interesting discussion today about multiple databases each containing large amounts of read-only data.  If that read-only data is common, then it would make sense to have a single copy of that data and have both databases share it.

Well, as long as you can isolate that data into its own tablespace, then you can do that easily with Oracle by transporting the metadata between two databases and leaving the files in place.

Here’s an example

Source database


SQL> select banner from v$version;

BANNER
--------------------------------------------------------------------------------
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
PL/SQL Release 12.1.0.2.0 - Production
CORE    12.1.0.2.0      Production
TNS for 64-bit Windows: Version 12.1.0.2.0 - Production
NLSRTL Version 12.1.0.2.0 - Production

SQL> create tablespace i_am_on_121 datafile 'C:\oracle\oradata\tts\my_tspace' size 50m;

Tablespace created.

SQL> create table t tablespace i_am_on_121 as select * from dba_objects;

Table created.

SQL> alter tablespace i_am_on_121 read only;

Tablespace altered.

C:\>expdp transport_tablespaces=i_am_on_121 directory=TEMP dumpfile=tts.dmp

Export: Release 12.1.0.2.0 - Production on Fri Apr 14 08:50:24 2017

Copyright (c) 1982, 2016, Oracle and/or its affiliates.  All rights reserved.

Username: mcdonac/*****

Connected to: Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options
Starting "MCDONAC"."SYS_EXPORT_TRANSPORTABLE_01":  mcdonac/******** transport_tablespaces=i_am_on_121 directory=TEMP dumpfile=tts.dmp
Processing object type TRANSPORTABLE_EXPORT/PLUGTS_BLK
Processing object type TRANSPORTABLE_EXPORT/TABLE
Processing object type TRANSPORTABLE_EXPORT/TABLE_STATISTICS
Processing object type TRANSPORTABLE_EXPORT/STATISTICS/MARKER
Processing object type TRANSPORTABLE_EXPORT/POST_INSTANCE/PLUGTS_BLK
Master table "MCDONAC"."SYS_EXPORT_TRANSPORTABLE_01" successfully loaded/unloaded
******************************************************************************
Dump file set for MCDONAC.SYS_EXPORT_TRANSPORTABLE_01 is:
  C:\TEMP\TTS.DMP
******************************************************************************
Datafiles required for transportable tablespace I_AM_ON_121:
  C:\ORACLE\ORADATA\TTS\MY_TSPACE
Job "MCDONAC"."SYS_EXPORT_TRANSPORTABLE_01" successfully completed at Fri Apr 14 08:51:16 2017 elapsed 0 00:00:47

and then we import it into a different database (and this one even is a different version!).

Target database


C:\Users\hamcdc>impdp transport_datafiles=C:\oracle\oradata\tts\my_tspace directory=TEMP dumpfile=tts.dmp

Import: Release 12.2.0.1.0 - Production on Fri Apr 14 08:51:28 2017

Copyright (c) 1982, 2017, Oracle and/or its affiliates.  All rights reserved.

Username: mcdonac/*****

Connected to: Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
Master table "MCDONAC"."SYS_IMPORT_TRANSPORTABLE_01" successfully loaded/unloaded
Starting "MCDONAC"."SYS_IMPORT_TRANSPORTABLE_01":  mcdonac/******** transport_datafiles=C:\oracle\oradata\tts\my_tspace directory=TEMP dumpfile=tts.dmp
Processing object type TRANSPORTABLE_EXPORT/PLUGTS_BLK
Processing object type TRANSPORTABLE_EXPORT/TABLE
Processing object type TRANSPORTABLE_EXPORT/TABLE_STATISTICS
Processing object type TRANSPORTABLE_EXPORT/STATISTICS/MARKER


SQL> select banner from v$version;

BANNER
--------------------------------------------------------------------------------
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
PL/SQL Release 12.2.0.1.0 - Production
CORE    12.2.0.1.0      Production
TNS for 64-bit Windows: Version 12.2.0.1.0 - Production
NLSRTL Version 12.2.0.1.0 - Production

SQL> select count(*) from t;

  COUNT(*)
----------
     92934

SQL> select * from dba_tablespaces
  2  where tablespace_name = 'I_AM_ON_121'
  3  @pr
==============================
TABLESPACE_NAME               : I_AM_ON_121
BLOCK_SIZE                    : 8192
INITIAL_EXTENT                : 65536
NEXT_EXTENT                   :
MIN_EXTENTS                   : 1
MAX_EXTENTS                   : 2147483645
MAX_SIZE                      : 2147483645
PCT_INCREASE                  :
MIN_EXTLEN                    : 65536
STATUS                        : READ ONLY
CONTENTS                      : PERMANENT
LOGGING                       : LOGGING
FORCE_LOGGING                 : NO
EXTENT_MANAGEMENT             : LOCAL
ALLOCATION_TYPE               : SYSTEM
PLUGGED_IN                    : YES
SEGMENT_SPACE_MANAGEMENT      : AUTO
DEF_TAB_COMPRESSION           : DISABLED
RETENTION                     : NOT APPLY
BIGFILE                       : NO
PREDICATE_EVALUATION          : HOST
ENCRYPTED                     : NO
COMPRESS_FOR                  :
DEF_INMEMORY                  : DISABLED
DEF_INMEMORY_PRIORITY         :
DEF_INMEMORY_DISTRIBUTE       :
DEF_INMEMORY_COMPRESSION      :
DEF_INMEMORY_DUPLICATE        :
SHARED                        : SHARED
DEF_INDEX_COMPRESSION         : DISABLED
INDEX_COMPRESS_FOR            :
DEF_CELLMEMORY                :
DEF_INMEMORY_SERVICE          :
DEF_INMEMORY_SERVICE_NAME     :
LOST_WRITE_PROTECT            : OFF
CHUNK_TABLESPACE              : N

PL/SQL procedure successfully completed.

12c Release 2, set feedback enhancement in SQL PLus

There’s a nice little touch to the “set feedback” command in SQL PLus in 12.2. There is a new “only” clause in the SET FEEDBACK command, so you can run queries but the resulting rows are not shown in the display. They are still queried, fetched and “returned”, but just rendered to the screen. Here’s an example


$ sqlplus hr/hr

SQL*Plus: Release 12.2.0.1.0 Production on Tue Mar 14 22:59:15 2017

Copyright (c) 1982, 2016, Oracle.  All rights reserved.

Last Successful login time: Sat Mar 11 2017 01:59:20 -04:00

Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

SQL> select * from regions;

 REGION_ID REGION_NAME
---------- -------------------------
         1 Europe
         2 Americas
         3 Asia
         4 Middle East and Africa

So that’s normal behaviour. Let’s now use the new ONLY option.


SQL> set feedback only 
SQL> select * from regions;

4 rows selected.

So why would you want that ? Well, sometimes you just want to run the query so that you can use a subsequent DBMS_XPLAN.DISPLAY_CURSOR call to see the true execution plan. Or perhaps, you just to want to examine some options with regard to the fetch performance. For example, here’s a demo of fetching from a large table called EMP


SQL> show arraysize
arraysize 10

SQL> set timing on
SQL> select * from emp;

1753088 rows selected.

Elapsed: 00:00:26.27

So that took 26 seconds, with an arraysize of 10. Let’s see if we can do better than that – we’ll bump up the arraysize to 200


SQL> set arraysize 200
SQL> select * from emp;

1753088 rows selected.

Elapsed: 00:00:04.65

Wow, thats pretty cool. Six times faster just by tweaking the batch size of the fetch. Surely then we can just keep bumping it up.


SQL> set arraysize 5000
SQL> select * from emp;

1753088 rows selected.

Elapsed: 00:00:04.43

Apparently not. There is a “sweet spot” for arraysize, and diminishing returns on performance when you go higher and higher (at the cost of consuming memory and resources on your client machine to drag all those rows down at once). But this post isn’t about arraysize, it’s merely a conduit for the nice cool feature SET FEEDBACK ONLY which lets us now test out such things without having to see all the rows presented back.

12c Release 2 – Transparent Data Encryption online !

It doesn’t take a rocket scientist to know that even if you have incredibly stringent controls on user authentication, user authorisation etc, that wont save you if your data on disk is not encrypted.  All you need is an errant tape, a missing disk, a misplaced flash stick…and kersplat, someone has a copy of your datafiles from your Oracle database.

Data at rest should be encrypted, but that often meant taking applications offline to do so.

I’ve put my Speed Racer hat on Smile and here’s a video on a new 12c Release 2 feature covered in 60 seconds !

Oracle Database 12c Release 2 is here !

image

Since OpenWorld 2016 when we first saw some of the cool features in Oracle Database 12c Release 2, many IT professionals out there have been exploring the release via our various cloud offerings, but if your organization has not yet embraced the cloud, then March 2017 is a great month for you !  Because you can now download the latest and greatest release of our database from the usual downloads page, and run it on your own servers in your own data centre.

Of course, there’s a difference between downloading and installing the software, and being up to speed with all of the great features that have come in 12c and 12c Release 2 so keep an eye on my blog, and on my YouTube channel.

Over the coming weeks I’ll be talking about lots of the new features in 12.2 in a short easy to digest videos to help you appreciate all of the goodness that is 12c Release 2 Smile

To whet your appetite, how cool is this simple enhancement to SQL Plus – command history !



SQL> history
  1  select * from dba_users where username = 'SYSTEM';
  2  select count(*)
     from dba_tables
     where table_Name like 'A%';
  3  select * from tab;
  4  show sga
  5  set timing off
  6  select * from dba_tablespaces;

SQL> history 4 run

Total System Global Area 1048576000 bytes
Fixed Size                  8795840 bytes
Variable Size             251660608 bytes
Database Buffers          784334848 bytes
Redo Buffers                3784704 bytes