UNDO TABLESPACE

Undo – Written on Blue Keyboard Key. Male Hand Presses Button on Black PC Keyboard. Closeup View. Blurred Background. 3D Render.
Undo tablespace check undo tablespace:
SQL> show parameter undo_tablespace;

NAME                                    TYPE              VALUE
------------------------------------ ----------- ------------------------------
undo_tablespace                        string            UNDOTBS1

Check to undo retention:

SQL> show parameter undo_retention;

NAME                                    TYPE             VALUE
------------------------------------ ----------- ------------------------------
undo_retention                         integer            900

Check to undo management:

SQL> show parameter undo_management;

NAME                                     TYPE                   VALUE
------------------------------------ ----------- ------------------------------
undo_management                          string                  AUTO

create new undo tablespace

SQL> create undo tablespace undotbs2 datafile '/u01/app/oracle/oradata/ORACLEAGENT/undo2.dbf' size 100m;

Tablespace created.

change undo tablespace

SQL> alter system set undo_tablespace='undotbs2' scope=spfile; 
System altered.

SQL> show parameter undo_tablespace;

NAME                                   TYPE               VALUE
------------------------------------ ----------- ------------------------------
undo_tablespace                        string            UNDOTBS1
SQL> shut immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.

SQL> startup
ORACLE instance started.

Total System Global Area 1610609200 bytes 
Fixed Size 8897072 bytes
Variable Size 385875968 bytes 
Database Buffers 1207959552 bytes 
Redo Buffers 7876608 bytes
 Database mounted.
Database opened.
SQL> show parameter undo_tablespace;

NAME                                   TYPE             VALUE
------------------------------------ ----------- ------------------------------
undo_tablespace                        string           undotbs2 



change undo_retention

SQL> show parameter undo_retention;

NAME                                    TYPE              VALUE
------------------------------------ ----------- ------------------------------
undo_retention                         integer             900

SQL> alter system set undo_retention=920;
System altered.

SQL> show parameter undo_retention; 

NAME                                    TYPE           VALUE
------------------------------------ ----------- ------------------------------
undo_retention                        integer           920 

check db block size

SQL> show parameter db_block_size;

NAME                                     TYPE              VALUE
------------------------------------ ----------- ------------------------------
db_block_size                            integer           8192

change undo management { auto | manual }

SQL> show parameter undo_management;
 NAME                                  TYPE               VALUE
------------------------------------ ----------- ------------------------------
undo_management                       string             MANUAL

SQL> alter system set undo_management='auto' scope=spfile; 
System altered.

SQL> shut immediate; 
Database closed.
Database dismounted. 
ORACLE instance shut down.

SQL> startup
ORACLE instance started.
Total System Global Area 1610609200 bytes 
Fixed Size 8897072 bytes
Variable Size 385875968 bytes 
Database Buffers 1207959552 bytes 
Redo Buffers 7876608 bytes 
Database mounted.
Database opened.

SQL> show parameter undo_management;

NAME                                   TYPE            VALUE
------------------------------------ ----------- ------------------------------
undo_management                        string         AUTO
Undo stages:
SQL> select tablespace_name tablespace, status, sum(bytes)/1024/1024 sum_in_mb, 
count(*) counts from dba_undo_extents group by tablespace_name, status order by 1,2;

TABLESPACE                      STATUS    SUM_IN_MB   COUNTS
------------------------------ --------- ---------- ----------
UNDOTBS1                        EXPIRED      1399.25     200
UNDOTBS1                        UNEXPIRED    168         21
UNDOTBS2                        EXPIRED      .375        6
UNDOTBS2                        UNEXPIRED     5.4375     42

Active, expired and unexpired transaction space usage in Undo Tablespace:-

ACTIVE: Status shows us the active transaction going in the database, utilizing the undo tablespace and cannot be truncated.

EXPIRED: Status shows us the transaction which is completed and complete the undo_retention time and now the first candidate for truncated from undo tablespace.

UNEXPIRED: Status shows us the transaction which is completed but not completed the undo retention time. It can be truncated if required.

Free blocks : At the time of creating new undo tablespace shows empty blocks

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Oracle Zero Downtime Migration 21c

Zero Downtime Migration (ZDM) 21c is available for download! ZDM is Oracle’s premier solution for moving your on-premises Oracle Database workloads to Oracle Cloud, supporting a variety of Oracle Database versions as the source and most Oracle Cloud Database Services as targets. Zero Downtime Migration 21c enhances the existing functionality by adding the long-requested Logical Migration workflow, which provides even more zero downtime migration choices!

For more reference: blogs.oracle.com click the below link

Oracle Zero Downtime Migration 21c

Logical Migration

In addition to the Physical Migration workflow which has been supported since the first version of ZDM (see for example: https://blogs.oracle.com/maa/announcing-oracle-zero-downtime-migration-release-197), ZDM 21c offers a Logical Migration to the Oracle Cloud in eight simple steps, which can be scheduled and monitored as needed. The Logical Migration workflow allows you to migrate to Oracle Autonomous Database leveraging ZDM automation.

You can leverage two logical migration workflows with different methodologies:

  • Logical Offline Migration
    • Data Pump and Database Links based methodology
    • Data Pump and Backup Location based methodology
  • Logical Online Migration
    • GoldenGate, Data Pump and Database Links based methodology
    • GoldenGate, Data Pump and Backup Location based methodology

Exadata On-Premises Support

Oracle ZDM 21c includes Exadata Database Machine as a new target. You can now migrate your current database deployments to an on-premises Exadata Database Machine, leveraging the full automation and power of ZDM. Migration to Exadata On-Premises is only supported via ZDM’s physical migration workflow.

Autonomous Database Support

Oracle ZDM 21c can now migrate databases directly to Autonomous Database using any of the logical migration workflows. Supported targets are:

  • Autonomous Transaction Processing (Shared & Dedicated)
  • Autonomous Data Warehouse (Shared & Dedicated)
  • Autonomous Database on Exadata Cloud at Customer

Non-CDB to CDB Migration Support

Non-CDB to CDB Migration is now supported in both Oracle ZDM’s physical and logical migration workflows, providing you with more migration flexibility via a simplified migration process that includes the Non-CDB to PDB conversion and hence, a wider choice of cloud targets.

Pre-Migration Advisor

A pre-migration advisor that evaluates the source database for feature compatibility and other limits is now included in the logical migration workflow only. You should leverage this advisor in order to better prepare for your database migration journey.

Support for Database Links

Logical Database Migration offers the possibility to establish direct Database Links between the source and the target, thus avoiding the need for a backup location as part of the migration workflow. Support for Database Links is optional, as you can also leverage a backup location such as Object Storage, NFS or the Recovery Appliance for your migration. Database Links based migration is not supported for Autonomous Database Dedicated.

Lighter ZDM Home

The Oracle ZDM software home is now lighter and more compact. Users will notice the difference already when downloading the binaries. ZDM installation and deployment has also been optimized and trimmed, allowing for an even faster instantiation of your first migration.

 

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Get ACL details in database

set lines 200
COL ACL_OWNER FOR A12
COL ACL FOR A67
COL HOST FOR A34
col PRINCIPAL for a20
col PRIVILEGE for a13
select ACL_OWNER,ACL,HOST,LOWER_PORT,UPPER_PORT FROM dba_network_acls;
select ACL_OWNER,ACL,PRINCIPAL,PRIVILEGE from dba_network_acl_privileges;

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How to Find the optimal undo retention size in database

SELECT d.undo_size / (1024 * 1024) “ACTUAL UNDO SIZE [MByte]”,
SUBSTR(e.value, 1, 25) “UNDO RETENTION [Sec]”,
(TO_NUMBER(e.value) * TO_NUMBER(f.value) * g.undo_block_per_sec) /
(1024 * 1024) “NEEDED UNDO SIZE [MByte]”
FROM (SELECT SUM(a.bytes) undo_size
FROM gv$datafile a, gv$tablespace b, dba_tablespaces c
WHERE c.contents = ‘UNDO’
AND c.status = ‘ONLINE’
AND b.name = c.tablespace_name
AND a.ts# = b.ts#) d,
gv$parameter e,
gv$parameter f,
(SELECT MAX(undoblks / ((end_time – begin_time) * 3600 * 24)) undo_block_per_sec
FROM v$undostat) g
WHERE e.name = ‘undo_retention’
AND f.name = ‘db_block_size’;

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Find who locked your account

— Return code 1017 ( INVALID LOGIN ATTEMPT)
— Return code 28000 ( ACCOUNT LOCKED)
set pagesize 1299
set lines 299
col username for a15
col userhost for a13
col timestamp for a39
col terminal for a23
SELECT username,userhost,terminal,timestamp,returncode
FROM dba_audit_session
WHERE username=’&USER_NAME’ and returncode in (1017,28000);

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Find active transactions in db

col name format a10
col username format a8
col osuser format a8
col start_time format a17
col status format a12
tti ‘Active transactions’

select s.sid,username,t.start_time, r.name, t.used_ublk “USED BLKS”,
decode(t.space, ‘YES’, ‘SPACE TX’,
decode(t.recursive, ‘YES’, ‘RECURSIVE TX’,
decode(t.noundo, ‘YES’, ‘NO UNDO TX’, t.status)
)) status
from sys.v_$transaction t, sys.v_$rollname r, sys.v_$session s
where t.xidusn = r.usn
and t.ses_addr = s.saddr
/

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