Performing common system tasks for Oracle DB instances - Amazon Relational Database Service

Performing common system tasks for Oracle DB instances

Following, you can find how to perform certain common DBA tasks related to the system on your Amazon RDS DB instances running Oracle. To deliver a managed service experience, Amazon RDS doesn't provide shell access to DB instances, and restricts access to certain system procedures and tables that require advanced privileges.

Disconnecting a session

To disconnect the current session by ending the dedicated server process, use the Amazon RDS procedure rdsadmin.rdsadmin_util.disconnect. The disconnect procedure has the following parameters.

Parameter name Data type Default Required Description

sid

number

Yes

The session identifier.

serial

number

Yes

The serial number of the session.

method

varchar

'IMMEDIATE'

No

Valid values are 'IMMEDIATE' or 'POST_TRANSACTION'.

The following example disconnects a session.

begin rdsadmin.rdsadmin_util.disconnect( sid => sid, serial => serial_number); end; /

To get the session identifier and the session serial number, query the V$SESSION view. The following example gets all sessions for the user AWSUSER.

SELECT SID, SERIAL#, STATUS FROM V$SESSION WHERE USERNAME = 'AWSUSER';

The database must be open to use this method. For more information about disconnecting a session, see ALTER SYSTEM in the Oracle documentation.

Terminating a session

To terminate a session, use the Amazon RDS procedure rdsadmin.rdsadmin_util.kill. The kill procedure has the following parameters.

Parameter name Data type Default Required Description

sid

number

Yes

The session identifier.

serial

number

Yes

The serial number of the session.

method

varchar

null

No

Valid values are 'IMMEDIATE' or 'PROCESS'.

The following example terminates a session.

begin rdsadmin.rdsadmin_util.kill( sid => sid, serial => serial_number); end; /

To get the session identifier and the session serial number, query the V$SESSION view. The following example gets all sessions for the user AWSUSER.

SELECT SID, SERIAL#, STATUS FROM V$SESSION WHERE USERNAME = 'AWSUSER';

You can specify either IMMEDIATE or PROCESS as a value for the method parameter. By specifying PROCESS as the method value, you can terminate the processes associated with a session. Do this only if terminating the session using IMMEDIATE as the method value was unsuccessful.

Canceling a SQL statement in a session

To cancel a SQL statement in a session, use the Amazon RDS procedure rdsadmin.rdsadmin_util.cancel.

Note

This procedure is supported for Oracle Database 19c and later.

The cancel procedure has the following parameters.

Parameter name Data type Default Required Description

sid

number

Yes

The session identifier.

serial

number

Yes

The serial number of the session.

sql_id

varchar2

null

No

The SQL identifier of the SQL statement.

The following example cancels a SQL statement in a session.

begin rdsadmin.rdsadmin_util.cancel( sid => sid, serial => serial_number, sql_id => sql_id); end; /

To get the session identifier, the session serial number, and the SQL identifier of a SQL statement, query the V$SESSION view. The following example gets all sessions and SQL identifiers for the user AWSUSER.

select SID, SERIAL#, SQL_ID, STATUS from V$SESSION where USERNAME = 'AWSUSER';

Enabling and disabling restricted sessions

To enable and disable restricted sessions, use the Amazon RDS procedure rdsadmin.rdsadmin_util.restricted_session. The restricted_session procedure has the following parameters.

Parameter name Data type Default Yes Description

p_enable

boolean

true

No

Set to true to enable restricted sessions, false to disable restricted sessions.

The following example shows how to enable and disable restricted sessions.

/* Verify that the database is currently unrestricted. */ SELECT LOGINS FROM V$INSTANCE; LOGINS ------- ALLOWED /* Enable restricted sessions */ EXEC rdsadmin.rdsadmin_util.restricted_session(p_enable => true); /* Verify that the database is now restricted. */ SELECT LOGINS FROM V$INSTANCE; LOGINS ---------- RESTRICTED /* Disable restricted sessions */ EXEC rdsadmin.rdsadmin_util.restricted_session(p_enable => false); /* Verify that the database is now unrestricted again. */ SELECT LOGINS FROM V$INSTANCE; LOGINS ------- ALLOWED

Flushing the shared pool

To flush the shared pool, use the Amazon RDS procedure rdsadmin.rdsadmin_util.flush_shared_pool. The flush_shared_pool procedure has no parameters.

The following example flushes the shared pool.

EXEC rdsadmin.rdsadmin_util.flush_shared_pool;

Flushing the buffer cache

To flush the buffer cache, use the Amazon RDS procedure rdsadmin.rdsadmin_util.flush_buffer_cache. The flush_buffer_cache procedure has no parameters.

The following example flushes the buffer cache.

EXEC rdsadmin.rdsadmin_util.flush_buffer_cache;

Granting SELECT or EXECUTE privileges to SYS objects

Usually you transfer privileges by using roles, which can contain many objects. To grant privileges to a single object, use the Amazon RDS procedure rdsadmin.rdsadmin_util.grant_sys_object. The procedure grants only privileges that the master user has already been granted through a role or direct grant.

The grant_sys_object procedure has the following parameters.

Important

For all parameter values, use uppercase unless you created the user with a case-sensitive identifier. For example, if you run CREATE USER myuser or CREATE USER MYUSER, the data dictionary stores MYUSER. However, if you use double quotes in CREATE USER "MyUser", the data dictionary stores MyUser.

Parameter name Data type Default Required Description

p_obj_name

varchar2

Yes

The name of the object to grant privileges for. The object can be a directory, function, package, procedure, sequence, table, or view. Object names must be spelled exactly as they appear in DBA_OBJECTS. Most system objects are defined in uppercase, so we recommend that you try that first.

p_grantee

varchar2

Yes

The name of the object to grant privileges to. The object can be a schema or a role.

p_privilege

varchar2

null

Yes

p_grant_option

boolean

false

No

Set to true to use the with grant option. The p_grant_option parameter is supported for 12.1.0.2.v4 and later, all 12.2.0.1 versions, and all 19.0.0 versions.

The following example grants select privileges on an object named V_$SESSION to a user named USER1.

begin rdsadmin.rdsadmin_util.grant_sys_object( p_obj_name => 'V_$SESSION', p_grantee => 'USER1', p_privilege => 'SELECT'); end; /

The following example grants select privileges on an object named V_$SESSION to a user named USER1 with the grant option.

begin rdsadmin.rdsadmin_util.grant_sys_object( p_obj_name => 'V_$SESSION', p_grantee => 'USER1', p_privilege => 'SELECT', p_grant_option => true); end; /

To be able to grant privileges on an object, your account must have those privileges granted to it directly with the grant option, or via a role granted using with admin option. In the most common case, you may want to grant SELECT on a DBA view that has been granted to the SELECT_CATALOG_ROLE role. If that role isn't already directly granted to your user using with admin option, then you can't transfer the privilege. If you have the DBA privilege, then you can grant the role directly to another user.

The following example grants the SELECT_CATALOG_ROLE and EXECUTE_CATALOG_ROLE to USER1. Since the with admin option is used, USER1 can now grant access to SYS objects that have been granted to SELECT_CATALOG_ROLE.

GRANT SELECT_CATALOG_ROLE TO USER1 WITH ADMIN OPTION; GRANT EXECUTE_CATALOG_ROLE to USER1 WITH ADMIN OPTION;

Objects already granted to PUBLIC do not need to be re-granted. If you use the grant_sys_object procedure to re-grant access, the procedure call succeeds.

Revoking SELECT or EXECUTE privileges on SYS objects

To revoke privileges on a single object, use the Amazon RDS procedure rdsadmin.rdsadmin_util.revoke_sys_object. The procedure only revokes privileges that the master account has already been granted through a role or direct grant.

The revoke_sys_object procedure has the following parameters.

Parameter name Data type Default Required Description

p_obj_name

varchar2

Yes

The name of the object to revoke privileges for. The object can be a directory, function, package, procedure, sequence, table, or view. Object names must be spelled exactly as they appear in DBA_OBJECTS. Most system objects are defined in upper case, so we recommend you try that first.

p_revokee

varchar2

Yes

The name of the object to revoke privileges for. The object can be a schema or a role.

p_privilege

varchar2

null

Yes

The following example revokes select privileges on an object named V_$SESSION from a user named USER1.

begin rdsadmin.rdsadmin_util.revoke_sys_object( p_obj_name => 'V_$SESSION', p_revokee => 'USER1', p_privilege => 'SELECT'); end; /

Granting privileges to non-master users

You can grant select privileges for many objects in the SYS schema by using the SELECT_CATALOG_ROLE role. The SELECT_CATALOG_ROLE role gives users SELECT privileges on data dictionary views. The following example grants the role SELECT_CATALOG_ROLE to a user named user1.

GRANT SELECT_CATALOG_ROLE TO user1;

You can grant EXECUTE privileges for many objects in the SYS schema by using the EXECUTE_CATALOG_ROLE role. The EXECUTE_CATALOG_ROLE role gives users EXECUTE privileges for packages and procedures in the data dictionary. The following example grants the role EXECUTE_CATALOG_ROLE to a user named user1.

GRANT EXECUTE_CATALOG_ROLE TO user1;

The following example gets the permissions that the roles SELECT_CATALOG_ROLE and EXECUTE_CATALOG_ROLE allow.

SELECT * FROM ROLE_TAB_PRIVS WHERE ROLE IN ('SELECT_CATALOG_ROLE','EXECUTE_CATALOG_ROLE') ORDER BY ROLE, TABLE_NAME ASC;

The following example creates a non-master user named user1, grants the CREATE SESSION privilege, and grants the SELECT privilege on a database named sh.sales.

CREATE USER user1 IDENTIFIED BY PASSWORD; GRANT CREATE SESSION TO user1; GRANT SELECT ON sh.sales TO user1;

Creating custom functions to verify passwords

You can create a custom password verification function in two ways. If you want to use standard verification logic, and to store your function in the SYS schema, use the create_verify_function procedure. If you want to use custom verification logic, or you don't want to store your function in the SYS schema, use the create_passthrough_verify_fcn procedure.

The create_verify_function procedure

The create_verify_function procedure is supported for version 12.1.0.2.v5 and later of Oracle Database 12c Release 1 (12.1), all Oracle Database 12c Release 2 (12.2.0.1) versions, and all Oracle Database 19c versions.

You can create a custom function to verify passwords by using the Amazon RDS procedure rdsadmin.rdsadmin_password_verify.create_verify_function. The create_verify_function procedure has the following parameters.

Parameter name Data type Default Required Description

p_verify_function_name

varchar2

Yes

The name for your custom function. This function is created for you in the SYS schema. You assign this function to user profiles.

p_min_length

number

8

No

The minimum number of characters required.

p_max_length

number

256

No

The maximum number of characters allowed.

p_min_letters

number

1

No

The minimum number of letters required.

p_min_uppercase

number

0

No

The minimum number of uppercase letters required.

p_min_lowercase

number

0

No

The minimum number of lowercase letters required.

p_min_digits

number

1

No

The minimum number of digits required.

p_min_special

number

0

No

The minimum number of special characters required.

p_min_different_chars

number

3

No

The minimum number of different characters required between the old and new password.

p_disallow_username

boolean

true

No

Set to true to disallow the user name in the password.

p_disallow_reverse

boolean

true

No

Set to true to disallow the reverse of the user name in the password.

p_disallow_db_name

boolean

true

No

Set to true to disallow the database or server name in the password.

p_disallow_simple_strings

boolean

true

No

Set to true to disallow simple strings as the password.

p_disallow_whitespace

boolean

false

No

Set to true to disallow white space characters in the password.

p_disallow_at_sign

boolean

false

No

Set to true to disallow the @ character in the password.

You can create multiple password verification functions.

There are restrictions on the name of your custom function. Your custom function can't have the same name as an existing system object. The name can be no more than 30 characters long. Also, the name must include one of the following strings: PASSWORD, VERIFY, COMPLEXITY, ENFORCE, or STRENGTH.

The following example creates a function named CUSTOM_PASSWORD_FUNCTION. The function requires that a password has at least 12 characters, 2 uppercase characters, 1 digit, and 1 special character, and that the password disallows the @ character.

begin rdsadmin.rdsadmin_password_verify.create_verify_function( p_verify_function_name => 'CUSTOM_PASSWORD_FUNCTION', p_min_length => 12, p_min_uppercase => 2, p_min_digits => 1, p_min_special => 1, p_disallow_at_sign => true); end; /

To see the text of your verification function, query DBA_SOURCE. The following example gets the text of a custom password function named CUSTOM_PASSWORD_FUNCTION.

COL TEXT FORMAT a150 SELECT TEXT FROM DBA_SOURCE WHERE OWNER = 'SYS' AND NAME = 'CUSTOM_PASSWORD_FUNCTION' ORDER BY LINE;

To associate your verification function with a user profile, use alter profile. The following example associates a verification function with the DEFAULT user profile.

ALTER PROFILE DEFAULT LIMIT PASSWORD_VERIFY_FUNCTION CUSTOM_PASSWORD_FUNCTION;

To see what user profiles are associated with what verification functions, query DBA_PROFILES. The following example gets the profiles that are associated with the custom verification function named CUSTOM_PASSWORD_FUNCTION.

SELECT * FROM DBA_PROFILES WHERE RESOURCE_NAME = 'PASSWORD' AND LIMIT = 'CUSTOM_PASSWORD_FUNCTION'; PROFILE RESOURCE_NAME RESOURCE LIMIT ------------------------- -------------------------------- -------- ------------------------ DEFAULT PASSWORD_VERIFY_FUNCTION PASSWORD CUSTOM_PASSWORD_FUNCTION

The following example gets all profiles and the password verification functions that they are associated with.

SELECT * FROM DBA_PROFILES WHERE RESOURCE_NAME = 'PASSWORD_VERIFY_FUNCTION'; PROFILE RESOURCE_NAME RESOURCE LIMIT ------------------------- -------------------------------- -------- ------------------------ DEFAULT PASSWORD_VERIFY_FUNCTION PASSWORD CUSTOM_PASSWORD_FUNCTION RDSADMIN PASSWORD_VERIFY_FUNCTION PASSWORD NULL

The create_passthrough_verify_fcn procedure

The create_passthrough_verify_fcn procedure is supported for version 12.1.0.2.v7 and later of Oracle Database 12c Release 1 (12.1), all Oracle Database 12c Release 2 (12.2) versions, and all Oracle Database 19c versions.

You can create a custom function to verify passwords by using the Amazon RDS procedure rdsadmin.rdsadmin_password_verify.create_passthrough_verify_fcn. The create_passthrough_verify_fcn procedure has the following parameters.

Parameter name Data type Default Required Description

p_verify_function_name

varchar2

Yes

The name for your custom verification function. This is a wrapper function that is created for you in the SYS schema, and it doesn't contain any verification logic. You assign this function to user profiles.

p_target_owner

varchar2

Yes

The schema owner for your custom verification function.

p_target_function_name

varchar2

Yes

The name of your existing custom function that contains the verification logic. Your custom function must return a boolean. Your function should return true if the password is valid and false if the password is invalid.

The following example creates a password verification function that uses the logic from the function named PASSWORD_LOGIC_EXTRA_STRONG.

begin rdsadmin.rdsadmin_password_verify.create_passthrough_verify_fcn( p_verify_function_name => 'CUSTOM_PASSWORD_FUNCTION', p_target_owner => 'TEST_USER', p_target_function_name => 'PASSWORD_LOGIC_EXTRA_STRONG'); end; /

To associate the verification function with a user profile, use alter profile. The following example associates the verification function with the DEFAULT user profile.

ALTER PROFILE DEFAULT LIMIT PASSWORD_VERIFY_FUNCTION CUSTOM_PASSWORD_FUNCTION;

Setting up a custom DNS server

Amazon RDS supports outbound network access on your DB instances running Oracle. For more information about outbound network access, including prerequisites, see Configuring outbound network access on your Oracle DB instance.

Amazon RDS Oracle allows Domain Name Service (DNS) resolution from a custom DNS server owned by the customer. You can resolve only fully qualified domain names from your Amazon RDS DB instance through your custom DNS server.

After you set up your custom DNS name server, it takes up to 30 minutes to propagate the changes to your DB instance. After the changes are propagated to your DB instance, all outbound network traffic requiring a DNS lookup queries your DNS server over port 53.

To set up a custom DNS server for your Amazon RDS for Oracle DB instance, do the following:

  • From the DHCP options set attached to your virtual private cloud (VPC), set the domain-name-servers option to the IP address of your DNS name server. For more information, see DHCP options sets.

    Note

    The domain-name-servers option accepts up to four values, but your Amazon RDS DB instance uses only the first value.

  • Ensure that your DNS server can resolve all lookup queries, including public DNS names, Amazon EC2 private DNS names, and customer-specific DNS names. If the outbound network traffic contains any DNS lookups that your DNS server can't handle, your DNS server must have appropriate upstream DNS providers configured.

  • Configure your DNS server to produce User Datagram Protocol (UDP) responses of 512 bytes or less.

  • Configure your DNS server to produce Transmission Control Protocol (TCP) responses of 1024 bytes or less.

  • Configure your DNS server to allow inbound traffic from your Amazon RDS DB instances over port 53. If your DNS server is in an Amazon VPC, the VPC must have a security group that contains inbound rules that permit UDP and TCP traffic on port 53. If your DNS server is not in an Amazon VPC, it must have appropriate firewall allow-listing to permit UDP and TCP inbound traffic on port 53.

    For more information, see Security groups for your VPC and Adding and removing rules.

  • Configure the VPC of your Amazon RDS DB instance to allow outbound traffic over port 53. Your VPC must have a security group that contains outbound rules that allow UDP and TCP traffic on port 53.

    For more information, see Security groups for your VPC and Adding and removing rules.

  • The routing path between the Amazon RDS DB instance and the DNS server has to be configured correctly to allow DNS traffic.

    • If the Amazon RDS DB instance and the DNS server are not in the same VPC, a peering connection has to be set up between them. For more information, see What is VPC peering?

Setting and unsetting system diagnostic events

To set and unset diagnostic events at the session level, you can use the Oracle SQL statement ALTER SESSION SET EVENTS. However, to set events at the system level you can't use Oracle SQL. Instead, use the system event procedures in the rdsadmin.rdsadmin_util package. The system event procedures are available in the following engine versions:

Important

Internally, the rdsadmin.rdsadmin_util package sets events by using the ALTER SYSTEM SET EVENTS statement. This ALTER SYSTEM statement isn't documented in the Oracle Database documentation. Some system diagnostic events can generate large amounts of tracing information, cause contention, or affect database availability. We recommend that you test specific diagnostic events in your nonproduction database, and only set events in your production database under guidance of Oracle Support.

Listing allowed system diagnostic events

To list the system events that you can set, use the Amazon RDS procedure rdsadmin.rdsadmin_util.list_allowed_system_events. This procedure accepts no parameters.

The following example lists all system events that you can set.

SET SERVEROUTPUT ON EXEC rdsadmin.rdsadmin_util.list_allowed_system_events;

The following sample output lists event numbers and their descriptions. Use the Amazon RDS procedures set_system_event to set these events and unset_system_event to unset them.

604 - error occurred at recursive SQL level 942 - table or view does not exist 1401 - inserted value too large for column 1403 - no data found 1410 - invalid ROWID 1422 - exact fetch returns more than requested number of rows 1426 - numeric overflow 1427 - single-row subquery returns more than one row 1476 - divisor is equal to zero 1483 - invalid length for DATE or NUMBER bind variable 1489 - result of string concatenation is too long 1652 - unable to extend temp segment by in tablespace 1858 - a non-numeric character was found where a numeric was expected 4031 - unable to allocate bytes of shared memory ("","","","") 6502 - PL/SQL: numeric or value error 10027 - Specify Deadlock Trace Information to be Dumped 10046 - enable SQL statement timing 10053 - CBO Enable optimizer trace 10173 - Dynamic Sampling time-out error 10442 - enable trace of kst for ORA-01555 diagnostics 12008 - error in materialized view refresh path 12012 - error on auto execute of job 12504 - TNS:listener was not given the SERVICE_NAME in CONNECT_DATA 14400 - inserted partition key does not map to any partition 31693 - Table data object failed to load/unload and is being skipped due to error:
Note

The list of the allowed system events can change over time. To make sure that you have the most recent list of eligible events, use rdsadmin.rdsadmin_util.list_allowed_system_events.

Setting system diagnostic events

To set a system event, use the Amazon RDS procedure rdsadmin.rdsadmin_util.set_system_event. You can only set events listed in the output of rdsadmin.rdsadmin_util.list_allowed_system_events. The set_system_event procedure accepts the following parameters.

Parameter name Data type Default Required Description

p_event

number

Yes

The system event number. The value must be one of the event numbers reported by list_allowed_system_events.

p_level

number

Yes

The event level. See the Oracle Database documentation or Oracle Support for descriptions of different level values.

The procedure set_system_event constructs and runs the required ALTER SYSTEM SET EVENTS statements according to the following principles:

  • The event type (context or errorstack) is determined automatically.

  • A statement in the form ALTER SYSTEM SET EVENTS 'event LEVEL event_level' sets the context events. This notation is equivalent to ALTER SYSTEM SET EVENTS 'event TRACE NAME CONTEXT FOREVER, LEVEL event_level'.

  • A statement in the form ALTER SYSTEM SET EVENTS 'event ERRORSTACK (event_level)' sets the error stack events. This notation is equivalent to ALTER SYSTEM SET EVENTS 'event TRACE NAME ERRORSTACK LEVEL event_level'.

The following example sets event 942 at level 3, and event 10442 at level 10. Sample output is included.

SQL> SET SERVEROUTPUT ON SQL> EXEC rdsadmin.rdsadmin_util.set_system_event(942,3); Setting system event 942 with: alter system set events '942 errorstack (3)' PL/SQL procedure successfully completed. SQL> EXEC rdsadmin.rdsadmin_util.set_system_event(10442,10); Setting system event 10442 with: alter system set events '10442 level 10' PL/SQL procedure successfully completed.

Listing system diagnostic events that are set

To list the system events that are currently set, use the Amazon RDS procedure rdsadmin.rdsadmin_util.list_set_system_events. This procedure reports only events set at system level by set_system_event.

The following example lists the active system events.

SET SERVEROUTPUT ON EXEC rdsadmin.rdsadmin_util.list_set_system_events;

The following sample output shows the list of events, the event type, the level at which the events are currently set, and the time when the event was set.

942 errorstack (3) - set at 2020-11-03 11:42:27 10442 level 10 - set at 2020-11-03 11:42:41 PL/SQL procedure successfully completed.

Unsetting system diagnostic events

To unset a system event, use the Amazon RDS procedure rdsadmin.rdsadmin_util.unset_system_event. You can only unset events listed in the output of rdsadmin.rdsadmin_util.list_allowed_system_events. The unset_system_event procedure accepts the following parameter.

Parameter name Data type Default Required Description

p_event

number

Yes

The system event number. The value must be one of the event numbers reported by list_allowed_system_events.

The following example unsets events 942 and 10442. Sample output is included.

SQL> SET SERVEROUTPUT ON SQL> EXEC rdsadmin.rdsadmin_util.unset_system_event(942); Unsetting system event 942 with: alter system set events '942 off' PL/SQL procedure successfully completed. SQL> EXEC rdsadmin.rdsadmin_util.unset_system_event(10442); Unsetting system event 10442 with: alter system set events '10442 off' PL/SQL procedure successfully completed.