Resource Manager In Oracle

Manager (the Resource Manager) enables us to optimize resource allocation among the many concurrent database sessions.Although we can manage resources via profiles a better option is to use the resource manager, by creating resource plans which specify how much of our resources should go to the various consumer groups, we can prioritize users and jobs. The resource manager can kill long running jobs, switch jobs to higher priority all automatically, the DBA can also manually switch users between resource groups.

What Problems Does the Resource Manager Address?
When database resource allocation decisions are left to the operating system, we may encounter the following problems:

Excessive overhead  :  Excessive overhead results from operating system context switching between Oracle Database server processes when the number of server processes is high.

Inefficient scheduling  :  The operating system deschedules database servers while they hold latches, which is inefficient.

Inappropriate allocation of resources  :  The operating system distributes resources equally among all active processes and is unable to prioritize one task over another.

Inability to manage database-specific resources, such as parallel execution servers and active sessions

How Does the Resource Manager Address These Problems?

The Resource Manager helps to overcome these problems by allowing the database more control over how hardware resources are allocated. The Resource Manager enables us to classify sessions into groups based on session attributes, and to then allocate resources to those groups in a way that optimizes hardware utilization for our application environment.

With the Resource Manager, we can:

• Guarantee certain sessions a minimum amount of processing resources regardless of the load on the system and the number of users.
• Distribute available processing resources by allocating percentages of CPU time to different users and applications. In a data warehouse, a higher percentage can be given to ROLAP (relational online analytical processing) applications than to batch jobs.
• Limit the degree of parallelism of any operation performed by members of a group of users.
• Create an active session pool. An active session pool consists of a specified maximum number of user sessions allowed to be concurrently active within a group of users. The active session pool limits the total number of sessions actively competing for resources, thereby enabling active sessions to make faster progress.
• Manage runaway sessions or calls by detecting when they consume more than a specified amount of CPU or I/O. Such sessions can be automatically terminated or switched into a different (lower priority) group.
• Prevent the execution of operations that the optimizer estimates will run for a longer time than a specified limit.
• Limit the amount of time that a session can be idle. This can be further defined to mean only sessions that are blocking other sessions.

Example: A Simple Resource Plan

                     


There are four elements to the Database Resource Manager (DRM) :

1.) Resource Consumer Group   -  A resource consumer group is a collection of users with similar requirements for resource consumption. Users can be assigned to more than one resource consumer group, but each user's active session can only be assigned to one resource consumer group at a time. For example, I can construct separate consumer groups for OLTP users, one for decision support users and one for users who typically create ad hoc queries.

2.) Resource plan -  A resource plan can also have multiple subplans that specify a finer grain of resource allocation detail. For example, I can create two subplans for my OLTP users, one for high-volume users and one for lower-volume users. Note that a subplan can have more than one parent plan, but Oracle will not permit a subplan to "loop back" upon itself.

3.) Resource allocation method - dictates the specific method we choose to use to allocate resources like CPU.  

4.) Resource Plan Directive -  Resource plan directives allocate resources among the resource consumer groups in the resource plan. Essentially, directives connect resource consumer groups or subplans to their resource plans. There is at least one resource plan directive for each entry in the resource plan.

Resource plan directives use resource allocation methods to determine how the DRM will allocate resources to a resource consumer group or resource plan. Several allocation methods are available:

CPU  :  As its name implies, this method controls how much CPU utilization will be permitted to user sessions for different resource consumer groups within a specific resource plan. CPU utilization is parceled out in declining levels from 1 to 8, and percentages are used to assign how much CPU should be granted to each consumer group at each level. User sessions for a consumer group with the highest level will receive resources before sessions assigned to a lower level are allowed to receive resources, so this method provides a mechanism to insure the highest-priority sessions receive at least some CPU resources.

Automatic Consumer Group Switching :  In some circumstances, I would like to have a user session that has begun to consume too many resources get switched automatically to a lower priority (for example, an ad hoc query user starts a "not in our lifetime" query, or a user runs a large report during peak OLTP processing hours). Using this method, the DRM can be directed to automatically switch such a user session to a different resource consumer group if the session is actively consuming resources beyond a certain amount of time. Even more impressive, this method can estimate an approximate time for the completion of the query and switch the session to a different group before the query is executed.

Active Session Pool Queueing  :  In some cases, I would like to be able to limit the activity for some groups of users based upon their maximum number of active sessions. This method detects when a specified threshold of user sessions has been reached for a consumer group and queues sessions until a "slot" is available. This method can also detect if a queued task has exceeded a specified time threshold, automatically terminate the queued task and return an error.

Maximum Estimated Execution Time  :  The DRM can also be directed to terminate an operation that has exceeded a specified maximum execution time. DRM will terminate the session and return a trappable error.

Maximum Degree of Parallelism  :  The DRM can limit the maximum degree of parallel processing for any operation within the plan.

Undo Pool Quota  :  Finally, the DRM can be directed to monitor the amount of undo (i.e. rollback) space being used by a resource consumer group. When undo utilization reaches the specified threshold, the DRM will terminate the current DML generating the redo log entries; no other members of that consumer group will be allowed to continue DML operations until sufficient redo space is available.

For more detail and examples click the below scripts

http://www.datadisk.co.uk/html_docs/oracle/resource_manager.htm

http://www.rittmanmead.com/2010/01/oracle-database-resource-manager-and-obiee/

http://oradbpedia.com/wiki/DBMS_RESOURCE_MANAGER_-_Overview

http://download.oracle.com/docs/cd/B28359_01/server.111/b28310/dbrm001.htm


Enjoy   :-)

Auditing in Oracle

Auditing is the monitoring and recording of selected user database actions. Auditing is normally used to:

1.) Investigate suspicious activity. For example, if an unauthorized user is deleting data from tables,the security administrator might decide to audit all connections to the database and all successful and unsuccessful deletions of rows from all tables in the database.

2.) Monitor and gather data about specific database activities. For example, the database administrator can gather statistics about which tables are being updated, how many logical I/Os are performed, or how many concurrent users connect at peak times.

There are two distinct types of auditing

1.) Standard        ->>  auditing based on statement, privilege and object-level
2.) Fine-grained  ->>  auditing on a finer granule which is based on content i.e. value > 10,000

Standard Auditing is further classified into 3 levels of standards auditing.The following are 

 i.)    Statement    ->>  audit all actions on any type of object.
ii.)   Privilege       ->>  audit actions that stem from system privileges.
iii.)  Object-level ->>  specific audit actions like select, update, insert or delete.

For all 3 levels of auditing we can choose to audit by access (audit every time we access) or by session (audit only once per access during the session), we can also auditing on if the access was successful (whenever successful) or not (whenever not successful).

How to eanable auditing : 
Below are some basic methods for auditing : 

1.) AUDIT_SYS_OPERATION : This parameter audits the SYS and SYSDBA connections. when we enable the parameter audit_sys_operations the database will write a trace file of the session action to the udump directory. This parameter should be enables on ALL production databases. Here is the method of enabling auditing .

SQL> alter system set audit_sys_operations=true scope=spfile;
SQL> shut immediate
SQL> startup
SQL> sho parameter audit
NAME                                TYPE                       VALUE
------------------                -----------            --------------------------------------------------------------
audit_file_dest                string               D:\ORACLE\PRODUCT\10.2.0\ADMIN\NOIDA\ADUMP
audit_sys_operations     boolean           TRUE
audit_trail                       string               DB
We can audit sys and sysdba connections from event logfile .(eventvwr.msc)


2.) AUDIT_TRAIL  Parameter : This parameter audit SESSION, DCL, DDL, DML, Select statements to table AUD$ or OS files.This is the easiest and most common method of auditing an oracle database, and this parameter should be set on ALL production databases. The audit_trail parameter can take the following values :

none  = disables auditing
os      = records the information to a o/s file (uses parameter audit_file_dest for the file location)
db      = records the information in the database, use the view dba_audit_trail ( view accesses table sys.aud$ )   to display audit information.
db, extended   = as per the db value but also populates the sqlbind and sqltext clob columns
xml     = audits to the o/s file but in xml format (uses parameter audit_file_dest for the file location)
xml,extended  =  as per xml option but also populates the sqlbind and sqltext clob columns


A basic list of audit option are as : 


==>Turn off auditing : 
SQL> alter system set audit_trail=none scope=spfile;


==> Auditing written to o/s :
SQL> alter system set audit_file_dest='c:\oracle\auditing';
SQL> alter system set audit_trail=os scope=spfile;


Note: if the audit_file_dest is not set then the default location is $oracle_home/rdbms/audit/


To start auditing we can use the below (there are many more options than stated below)
==> On Session    
SQL> audit session by neer;


==> On Table 
SQL> audit table;


==>Table and Specific user   
SQL>audit table by neer;


==>Table, Specific User and Access
SQL> audit table by neer by access;

==>Privilege auditing
SQL>audit create any table;

SQL>audit create any table by neer;


==>Object auditing
SQL> audit select on neer.employees by access whenever successful;

SQL> audit select on neer.employees by access whenever not successful;


==>Disabling audit
SQL>noaudit table;
SQL>noaudit all privileges;
SQL>noaudit create any table by neer;


==>Turn off all auditing
SQL> noaudit all;                              (turn off all statement auditing)

SQL> noaudit all privileges;               (turn off all privilege auditing)
SQL> noaudit all on default;               (turn off all object auditing)


==>Purge audit table
SQL>delete from sys.aud$;
SQL>truncate from sys.aud$;


Here is demo of the Standard auditting  :


C:\>sqlplus / as sysdba
SQL*Plus: Release 10.2.0.1.0 - Production on Sat Jul 23 13:58:26 2011
Copyright (c) 1982, 2005, Oracle.  All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options


SQL> alter system set audit_trail=db scope=spfile;   
System altered.


SQL> shut immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.


Total System Global Area      167772160  bytes
Fixed Size                             1247876      bytes
Variable Size                         75498876    bytes
Database Buffers                   83886080    bytes
Redo Buffers                         7139328      bytes
Database mounted.
Database opened.
SQL> create user test identified by test
  2  default tablespace users
  3  quota unlimited on users;
User created.


SQL> grant connect to test;
Grant succeeded.


SQL> grant create table,create procedure to test;
Grant succeeded.


SQL> audit select table,update table,insert table,delete table by test by access;
Audit succeeded.


SQL> audit all by test by access;
Audit succeeded.


SQL> conn test/test@noida
Connected.


SQL> create table aud_table(id number);
Table created.


SQL> insert into aud_table values (&A);
Enter value for a: 1
old   1: insert into aud_table values (&A)
new   1: insert into aud_table values (1)
1 row created.


SQL> insert into aud_table values (&A);
Enter value for a: 2
old   1: insert into aud_table values (&A)
new   1: insert into aud_table values (2)
1 row created.


SQL> /
Enter value for a: 3
old   1: insert into aud_table values (&A)
new   1: insert into aud_table values (3)
1 row created.


SQL> update aud_table set id=123 where id=2;
1 row updated.


SQL> select  *  from aud_table;
        ID
----------
         1
       123
         3


SQL> delete from aud_table;
3 rows deleted.


SQL> drop table aud_table;
Table dropped.


SQL> conn / as sysdba
Connected.


SQL> select username,obj_name,action_name from dba_audit_trail
  2       where owner='TEST' order by timestamp;


USERNAME              OBJ_NAME             ACTION_NAME
---------                   ---------------           -------------------
TEST                      AUD_TABLE              CREATE TABLE
TEST                      AUD_TABLE              INSERT
TEST                      AUD_TABLE              INSERT
TEST                      AUD_TABLE              INSERT
TEST                      AUD_TABLE              UPDATE
TEST                      AUD_TABLE              SELECT
TEST                      AUD_TABLE              DELETE
TEST                      AUD_TABLE              DROP TABLE
8 rows selected.

FGA (fine-grained auditing)  :  Fine-grain auditing (FGA) allows us to audit users accessing data of a certain criteria. As per standard auditing we can audit select, insert, update and delete operations. We use the package dbms_fga to add, remove, enable and disable FGA auditing policies, it is virtually impossible to bypass these policies, one nice feature is that we can attach handlers (like a trigger) to the policies which can execute procedures.

There are many options that can be applied to the dbms_fga package, here are some simple examples : 
==> Creating  :  


SQL> begin
dbms_fga.add_policy (
object_schema=>'neer',
object_name=>'employees',
policy_name=>'aud_test',
audit_column=>'salary,commission_pct',
enable=>false,
statement_types=>'select'); 
end;
/


==> Removing  :  


SQL> begin
dbms_fga.drop_policy (
object_schema=>'neer',
object_name=>'employees',
policy_name=>'aud_test');
end;
/


==>Enabling  :  


SQL>begin
dbms_fga.enable_policy (
object_schema=>'neer',
object_name=>'employees',
policy_name=>'aud_test');
end;
/


==> Disabling  :


SQL> begin
dbms_fga.edisable_policy (
object_schema=>'neer',
object_name=>'employees',
policy_name=>'aud_test');
end;
/

Here is Demo of the FGA Auditing  :  

First,we will create the FGA policy say "FGA_AUD"

SQL>  begin
  2  dbms_fga.add_policy (
  3  object_schema=>'test',
  4  object_name=>'hot',
  5  policy_name=>'FGA_AUD',
  6  audit_column=>'id',
  7  enable=>true,
  8  statement_types=>'select,update');
  9  end;
 10  /
PL/SQL procedure successfully completed.

Now we will perform some "select" and "update" statements to audit  :

SQL> update hot set id=2222 where id=123;
0 rows updated.

SQL> update hot set id=2222 where id=2;
1 row updated.

SQL> select * from hot;
        ID
   ----------
       22
      2222
      2342

SQL> update hot set id=8888 where id=2342;
1 row updated.

SQL> commit;
Commit complete.

To audit the table and the statements fired by db_user, fire the below query :

SQL> select   db_user  ,scn,  sql_text   from  dba_fga_audit_trail   where   db_user='TEST';
db_user         SCN                        SQL_TEXT
--------        ----------              ------------------------------------
TEST          1186412              update hot set id=2222 where id=123
TEST          1186421              update hot set id=2222 where id=2
TEST          1186431              select * from hot
TEST          1186440              update hot set id=8888 where id=2342

SYS.AUD$ table :  Make sure that the sys.aud$ table gets purged from time to time as connections and DML activity in the database might come to a stand still if it becomes full.


 Purge Audit Table : 
SQL> delete from sys.aud$;
SQL> truncate from sys.aud$;   

For Schemas level auditing check here :



Enjoy   :-) 

Create Read-only user for a Schema

Sometimes the DBA requires  to create the read-only user for a particular schemas.While creating the user,one should always keep in mind that the user should have minimum privileges.  There is no any direct command to create the read-only user in oracle.Sometimes I find people grants  “read any table ”  privileges to create the read-only  user ,which is not correct . Here is demo for creating read-only users. 

In this demo, I have created a user name “neer” and given  access to select only  “hr”  schemas tables.

Step  1  :  Create User  “NEER”

SQL> create user neer identified by neer;

User created.

Step  2  :  Grant session and create synonym privileges

SQL> grant create session ,create synonym to  neer ;

Grant succeeded.

Step  3  :  Make script to grant  select privileges to neer 

Here I have created the script with the help of spool  by selecting the tables of the HR schemas .

SQL> SPOOL  C:\select_privs.sql

SQL> select 'grant select on hr.'||table_name|| '  to neer;' from dba_tables where owner='HR';

SQL> select 'grant select on hr.'||view_name||  '  to neer;' from dba_views where owner='HR';

SQL> spool off

Now , we will check the spool  “select _privs.sql”  and prepare this as script for grant permission.

Step  4  :  Run the script to grant the permission

SQL> @C:\select_privs.sql

The  script  “select_privs.sql”  script  after modification  is .

grant select on hr.REGIONS to neer;                                             

grant select on hr.LOCATIONS to neer;                                           

grant select on hr.DEPARTMENTS to neer;                                         

grant select on hr.JOBS to neer;                                                

grant select on hr.EMPLOYEES to neer;                                           

grant select on hr.JOB_HISTORY to neer;                                         

grant select on hr.COUNTRIES to neer;                                                                

grant select on hr.EMP_DETAILS_VIEW to neer;                                    

  

Step  5  :  Create the synonym    

Connect to “NEER” schemas and create the synonym so that the “NEER” user can access the “HR”  schemas without any  dot(.)  like  “select * from employees”   instead of   “select * from HR.employees” .Here again we use the above method.

SQL> conn neer/neer@noida

SQL> SPOOL  C:\synonym_privs.sql

SQL> select 'create synonym '||view_name|| '  for HR.'||view_name||';' from all_views where owner='HR';

SQL> select 'create synonym '||table_name|| '  for HR.'||table_name||';' from all_tables where owner='HR';

SQL> spool off

Now we have the script to create the synonym

SQL>@ C:\synonym_privs.sql

Now we have successfully created a read-only user for a particular schemas.

Step  6  :   Check the tables

SQL> select Count(*) from employees ;

  COUNT(*)

----------

       107

SQL> select Count(*) from hr.employees;

  COUNT(*)

----------

       107

SQL> sho user

USER is "NEER"

Enjoy   :-)