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In Oracle database management, tablespace operation is the foundation of the foundation. Among them, the tablespace Offline is the one we often come into contact with. Together with the data file Offline, it constitutes an important architecture for Oracle to maintain data consistency.

Generally speaking, what we often come into contact with is the direct alter tablespace xxx offline operation. But in practice, Oracle provides three offline parameters according to the different situations of the corresponding data files in the tablespace. Like several parameters corresponding to database shutdown shutdown, different offline parameters correspond to different behaviors of Oracle, which leads to different processing methods.

The following is the explanation of the tablespace offline in the Oracle11g official document:

*

You may want to take a tablespace offline for any of the following reasons:

To make a portion of the database unavailable while allowing normal access to the remainder of the databaseTo perform an offline tablespace backup (even though a tablespace can be backed up while online and in use) To make an application and its group of tables temporarily unavailable while updating or maintaining the applicationTo rename or relocate tablespace datafiles wants to make tablespaces offline for the following reasons:

? Make part of the database inaccessible while allowing normal access to the rest of the database

? To perform an offline tablespace backup (even if the tablespace can be backed up online and in use)

? Make the application and its set of tables temporarily unavailable when updating or maintaining the application

? Rename or relocate tablespace data files

When a tablespace is taken offline, the database takes all the associated files offline.

When the tablespace is offline, the database takes all associated files offline.

You cannot take the following tablespaces offline:

SYSTEMThe undo tablespaceTemporary tablespacesSYSTEM, undo and temporary tablespaces cannot be offline

Before taking a tablespace offline, consider altering the tablespace allocation of any users who have been assigned the tablespace as a default tablespace. Doing so is advisable because those users will not be able to access objects in the tablespace while it is offline.

Before taking the tablespace offline, consider changing the tablespace allocation of any user who has allocated the tablespace to the default tablespace. This is desirable because these users will not be able to access objects in the tablespace while offline.

You can specify any of the following parameters as part of the ALTER TABLESPACE...OFFLINE statement:

Clause

Description

NORMAL

A tablespace can be taken offline normally if no error conditions exist for any of the datafiles of the tablespace. No datafile in the tablespace can be currently offline as the result of a write error. When you specify OFFLINE NORMAL, the database takes a checkpoint for all datafiles of the tablespace as it takes them offline. NORMAL is the default.

1. Normal is the default mode of offline

2. Normal checkpoints all data files in the tablespace, and media recovery is not required for online tablespaces.

3. When the tablespace is offline in normal mode, there should be no write errors, and all files in the tablespace should be in online state.

TEMPORARY

A tablespace can be taken offline temporarily, even if there are error conditions for one or more files of the tablespace. When you specify OFFLINE TEMPORARY, the database takes offline the datafiles that are not already offline, checkpointing them as it does so.

If no files are offline, but you use the temporary clause, media recovery is not required to bring the tablespace back online. However, if one or more files of the tablespace are offline because of write errors, and you take the tablespace offline temporarily, the tablespace requires recovery before you can bring it back online.

1. When offline temporary tablespaces, if there is no offline data file in the tablespaces, media recovery is not required when online the tablespaces.

2. When offline temporary tablespaces, checkpointing operations are not performed on data files that have already been offline, but only on data files of online

3. When offline temporary tablespaces, for data files that have been offline before offline tablespaces, when online the tablespaces, offline data files need media recovery.

IMMEDIATE

A tablespace can be taken offline immediately, without the database taking a checkpoint on any of the datafiles. When you specify OFFLINE IMMEDIATE, media recovery for the tablespace is required before the tablespace can be brought online. You cannot take a tablespace offline immediately if the database is running in NOARCHIVELOGmode.

1. Offline immediate does not checkpoint any files in the tablespace.

2. Media recovery all data files when online tablespace

3. Offline immediate needs the database log mode to be archived.

Caution:

If you must take a tablespace offline, use the NORMAL clause (the default) if possible. This setting guarantees that the tablespace will not require recovery to come back online, even if after incomplete recovery you reset the redo log sequence using an ALTER DATABASE OPEN RESETLOGS statement.

If the tablespace must be taken offline, use the NORMAL clause (the default) whenever possible. This setting ensures that the tablespace does not need to be restored online, even after an incomplete recovery, using the ALTER DATABASE OPEN RESETLOGS statement to reset the redo log sequence.

Speify TEMPORARY only when you cannot take the tablespace offline normally. In this case, only the files taken offline because of errors need to be recovered before the tablespace can be brought online. Specify IMMEDIATE only after trying both the normal and temporary settings.

Specify TEMPORARY only if the tablespace cannot be taken offline normally. In this case, only files that are offline in the event of an error need to be restored before the tablespace goes online. Specify IMMEDIATE only after normal and temporary settings have been attempted.

The following example takes the users tablespace offline normally:

ALTER TABLESPACE users OFFLINE NORMAL

*

As described in the above official documentation, the command to Offline the tablespace is very simple, that is, alter tablespace xxx offline; can be decorated with three parameters, namely normal, temporary and immediate, depending on the situation. The three commands correspond to different behaviors of the Offline process.

In the following experiment, we use a specific case to distinguish the differences between the three command parameters:

Experimental environment:

(note: archiving mode is critical to data tablespace and file Offline behavior! )

SYS@seiang11g > select * from v$version

BANNER

Oracle Database 11g Enterprise Edition Release 11.2.0.4.0-64bit Production

PL/SQL Release 11.2.0.4.0-Production

CORE 11.2.0.4.0 Production

TNS for Linux: Version 11.2.0.4.0-Production

NLSRTL Version 11.2.0.4.0-Production

SYS@seiang11g > archive log list

Database log mode Archive Mode

Automatic archival Enabled

Archive destination / u01/app/oracle/arch

Oldest online log sequence 50

Next log sequence to archive 52

Current log sequence 52

Example 1: offline normal in archive mode

Create a tablespace wjqtest, which consists of two data files for more obvious experiments.

SYS@seiang11g > create tablespace wjqtest datafile'/ u01 size size

2 extent management local uniform size 1M

3 segment space management auto

Tablespace created.

SYS@seiang11g >

SYS@seiang11g > alter tablespace wjqtest add datafile'/ u01 size size

Tablespace altered.

SYS@seiang11g > select tablespace_name,status from dba_tablespaces where tablespace_name='WJQTEST'

TABLESPACE_NAME STATUS

WJQTEST ONLINE

SYS@seiang11g > select file_name,status,online_status from dba_data_files where tablespace_name='WJQTEST'

FILE_NAME STATUS ONLINE_

-

/ u01/app/oracle/oradata/OraDB11g/wjqtest01.dbf AVAILABLE ONLINE

/ u01/app/oracle/oradata/OraDB11g/wjqtest02.dbf AVAILABLE ONLINE

SCOTT@seiang11g > create table wjqtest tablespace wjqtest as select * from dba_objects where rownumselect count (*) from wjqtest

COUNT (*)

-

nine hundred and ninety nine

SYS@seiang11g > alter tablespace wjqtest offline normal

Tablespace altered.

SYS@seiang11g > select tablespace_name, status from dba_tablespaces where tablespace_name='WJQTEST'

TABLESPACE_NAME STATUS

WJQTEST OFFLINE

SYS@seiang11g > select file_name,status,online_status from dba_data_files where tablespace_name='WJQTEST'

FILE_NAME STATUS ONLINE_

-

/ u01/app/oracle/oradata/OraDB11g/wjqtest01.dbf AVAILABLE OFFLINE

/ u01/app/oracle/oradata/OraDB11g/wjqtest02.dbf AVAILABLE OFFLINE

[oracle@seiang11g trace] $tail-f alert_seiang11g.log

Tue Sep 26 13:19:22 2017

Alter tablespace wjqtest offline normal

Completed: alter tablespace wjqtest offline normal

Tue Sep 26 13:19:22 2017

Starting background process SMCO

Tue Sep 26 13:19:22 2017

SMCO started with pid=31, OS id=6497

Tue Sep 26 13:19:30 2017

Checker run found 3 new persistent data failures

A very important content of the data file is the SCN number of the data file header. We know that when shutting down the database or check point completely, Oracle is to ensure that the SCN of the control file is consistent with that of the data file header.

SYS@seiang11g > select file#, status, recover, fuzzy, checkpoint_change# from v$datafile_header

FILE# STATUS REC FUZ CHECKPOINT_CHANGE#

1 ONLINE NO YES 1860869

2 ONLINE NO YES 1860869

3 ONLINE NO YES 1860869

4 ONLINE NO YES 1860869

5 ONLINE NO YES 1860869

6 ONLINE NO YES 1860869

7 ONLINE NO YES 1860869

8 OFFLINE 0

9 OFFLINE 0

9 rows selected.

SYS@seiang11g >

SYS@seiang11g > select file#,checkpoint_change#,online_change# from v$datafile

FILE# CHECKPOINT_CHANGE# ONLINE_CHANGE#

1 1860869 925702

2 1860869 925702

3 1860869 925702

4 1860869 925702

5 1860869 951158

6 1860869 0

7 1860869 0

8 1862009 0

9 1862009 0

9 rows selected.

RMAN > list failure all

Using target database control file instead of recovery catalog

List of Database Failures

=

Failure ID Priority Status Time Detected Summary

--

254 HIGH OPEN 26-SEP-17 Tablespace 9: 'WJQTEST' is offline

222 HIGH OPEN 26-SEP-17 One or more non-system datafiles are offline

If it is a normal offline normal, you can directly online back to the normal tablespace.

SYS@seiang11g > alter tablespace wjqtest online

Tablespace altered.

SYS@seiang11g > select file#, status, recover, fuzzy, checkpoint_change# from v$datafile_header

FILE# STATUS REC FUZ CHECKPOINT_CHANGE#

1 ONLINE NO YES 1860869

2 ONLINE NO YES 1860869

3 ONLINE NO YES 1860869

4 ONLINE NO YES 1860869

5 ONLINE NO YES 1860869

6 ONLINE NO YES 1860869

7 ONLINE NO YES 1860869

8 ONLINE NO YES 1862119

9 ONLINE NO YES 1862119

9 rows selected.

SYS@seiang11g >

SYS@seiang11g > select file#,checkpoint_change#,online_change# from v$datafile

FILE# CHECKPOINT_CHANGE# ONLINE_CHANGE#

1 1860869 925702

2 1860869 925702

3 1860869 925702

4 1860869 925702

5 1860869 951158

6 1860869 0

7 1860869 0

8 1862119 1862119

9 1862119 1862119

9 rows selected.

[oracle@seiang11g trace] $tail-f alert_seiang11g.log

Tue Sep 26 13:21:47 2017

Alter tablespace wjqtest online

Completed: alter tablespace wjqtest online

RMAN > list failure all

No failures found that match specification

Under normal database conditions, the header SCN number of the data file cannot be maintained for performance reasons. After we use offline normal, each data file header SCN is the same. Therefore, the offline normal feature is in offline, to type check point on all files in the tablespace, as long as you can type the SCN number, offline normal can be completed normally. In other words, offline normal is the turn-off of file consistency across tablespaces.

Example 2: offline temporary in archive mode

Offline Normal is an ideal situation. In many cases, when Offline is a Tablespace, it cannot be executed successfully. For example, during offline operations, offline may be affected if there are ongoing DDL and DML operations on tablespace objects. In addition, if there is a data file in a table space that has been passed by Offline, we are normally not able to do offline normal. At this point, we need to use temporary.

We first offline one of the data files in the tablespace.

SYS@seiang11g > alter database datafile'/ u01 offline

Database altered.

Note: this operation can only be done in Archivelog mode. If you are in non-archive mode, a data file in the direct offline tablespace will have an ORA-01145 error as follows:

SYS@seiang11g > alter database datafile'/ u01 offline

Alter database datafile'/ u01 offline

*

ERROR at line 1:

ORA-01145: offline immediate disallowed unless media recovery enabled

SYS@seiang11g >! oerr ora 01145

01145, 00000, "offline immediate disallowed unless media recovery enabled"

/ / * Cause: ALTER TABLESPACE... OFFLINE IMMEDIATE or ALTER DATABASE DATAFILE

/ /... OFFLINE is only allowed if database is in ARCHIVELOG mode.

/ / * Action:Take tablespace offline normally or shutdown abort. Reconsider your

/ / backup strategy. You could do this if you were archiving your logs.

In order to offline data files, you must be in archive mode, which is a measure of Oracle automatic protection to prevent data files from being offline in non-archive mode, resulting in data loss.

Solution:

Can be in non-archive mode

Use the alter database datafile'/ u01/app/oracle/oradata/OraDB11g/wjqtest01.dbf 'offline for drop; statement to take the data file offline and drop does not delete the physical file. If you are not using alter system switch logfile; to switch log filegroups, you can use recover datafile XXX; to restore and go online. If you have switched the log filegroup and cleared its contents, the data file can no longer be brought back online and will always be in the recover state (which can be seen through the v$datafile view). So if in the actual production environment, try to do offline data file operation in archive mode.

SYS@seiang11g >

SYS@seiang11g > select tablespace_name,status from dba_tablespaces where tablespace_name='WJQTEST'

TABLESPACE_NAME STATUS

WJQTEST ONLINE

Observing the table space and data file status, it is found that the data file status of the offline is Recover.

SYS@seiang11g > select file_name,status,online_status from dba_data_files where tablespace_name='WJQTEST'

FILE_NAME STATUS ONLINE_

-

/ u01/app/oracle/oradata/OraDB11g/wjqtest01.dbf AVAILABLE RECOVER

/ u01/app/oracle/oradata/OraDB11g/wjqtest02.dbf AVAILABLE ONLINE

The recover status of the file you see indicates that you need to Recover if you need the file to return to the Online state. At this point, the states of several files under the Online status table space are inconsistent.

Note that Oracle maintains data file consistency, which is a dynamic consistency process. If a file or object temporarily exits the consistency mechanism, it means that the file or object is no longer consistent. If the object wants to return to the original consistency system, it needs to do Recover. The Recover means of Oracle requires the help of continuous redo log files.

Try using offline normal tablespaces

SYS@seiang11g > alter tablespace wjqtest offline normal

Alter tablespace wjqtest offline normal

*

ERROR at line 1:

ORA-01191: file 8 is already offline-cannot do a normal offline

ORA-01110: data file 8:'/ u01qqtest01.dbf'

SCOTT@seiang11g > create table tb_test tablespace wjqtest as select * from dba_objects where 1: 0

Table created.

[oracle@seiang11g trace] $tail-f alert_seiang11g.log

Tue Sep 26 13:26:53 2017

Alter tablespace wjqtest offline normal

ORA-1191 signalled during: alter tablespace wjqtest offline normal...

Tue Sep 26 13:26:53 2017

Checker run found 1 new persistent data failures

Normal normal offline is no longer successful. The temporary parameter can be used at this point.

SYS@seiang11g > alter tablespace wjqtest offline temporary

Tablespace altered.

SYS@seiang11g >

SYS@seiang11g > select tablespace_name,status from dba_tablespaces where tablespace_name='WJQTEST'

TABLESPACE_NAME STATUS

WJQTEST OFFLINE

SYS@seiang11g >

SYS@seiang11g > select file_name,status,online_status from dba_data_files where tablespace_name='WJQTEST'

FILE_NAME STATUS ONLINE_

-

/ u01/app/oracle/oradata/OraDB11g/wjqtest01.dbf AVAILABLE RECOVER

/ u01/app/oracle/oradata/OraDB11g/wjqtest02.dbf AVAILABLE OFFLINE

[oracle@seiang11g trace] $tail-f alert_seiang11g.log

Tue Sep 26 13:30:01 2017

Alter tablespace wjqtest offline temporary

Completed: alter tablespace wjqtest offline temporary

Tue Sep 26 13:30:15 2017

Checker run found 2 new persistent data failures

Offline is implemented using the temporary parameter. But for the data file that offline ahead of time, the status is still recover. Presumably, the Temporary Offline process is an inconsistent shutdown.

The view views v$datafile and v$datafile_header reflect the record of the file SCN number in the control file and data file header. In offline normal, we saw the consistency of the various files. When doing offline normal, Oracle inserts a check point (internal) to synchronize the header SCN of each file.

What is the view state when using Temporary?

SYS@seiang11g > select file#, status, recover, fuzzy, checkpoint_change# from v$datafile_header

FILE# STATUS REC FUZ CHECKPOINT_CHANGE#

1 ONLINE NO YES 1860869

2 ONLINE NO YES 1860869

3 ONLINE NO YES 1860869

4 ONLINE NO YES 1860869

5 ONLINE NO YES 1860869

6 ONLINE NO YES 1860869

7 ONLINE NO YES 1860869

8 OFFLINE YES YES 1862119

9 OFFLINE NO NO 1862456

9 rows selected.

SYS@seiang11g >

SYS@seiang11g > select file#,checkpoint_change#,online_change# from v$datafile

FILE# CHECKPOINT_CHANGE# ONLINE_CHANGE#

1 1860869 925702

2 1860869 925702

3 1860869 925702

4 1860869 925702

5 1860869 951158

6 1860869 0

7 1860869 0

8 1862119 1862119

9 1862456 1862119

9 rows selected.

The SCN numbers of the two files above the control file and the data file header are different, indicating that the SCN number of the file within a tablespace is inconsistent.

Note: in Temporary Offline, some "problem" data files and "no problem" data files can be different. "No problem" data files have the same SCN number.

If you directly Online the tablespace at this time, the error ORA-01113 and ORA-01110 will be reported.

SYS@seiang11g > alter tablespace wjqtest online

Alter tablespace wjqtest online

*

ERROR at line 1:

ORA-01113: file 8 needs media recovery

ORA-01110: data file 8:'/ u01qqtest01.dbf'

In online, Oracle must go to online a "consistent" tablespace. At this point, it finds inconsistencies in the SCN within the tablespace. According to the prompt, we need to recover the files manually.

SYS@seiang11g > recover datafile 8

Media recovery complete.

SYS@seiang11g > alter tablespace wjqtest online

Tablespace altered.

Online succeeded, and you saw the redo log apply and even archived redo log apply processes used in media recovery in the alert log. Note: we have only restored datafile 6 at this time.

[oracle@seiang11g trace] $tail-f alert_seiang11g.log

Tue Sep 26 13:34:05 2017

ALTER DATABASE RECOVER datafile 8

Media Recovery Start

Serial Media Recovery started

Recovery of Online Redo Log: Thread 1 Group 1 Seq 52 Reading mem 0

Mem# 0: / u01/app/oracle/oradata/OraDB11g/redo01.log

Media Recovery Complete (seiang11g)

Completed: ALTER DATABASE RECOVER datafile 8

SYS@seiang11g > select file#, status, recover, fuzzy, checkpoint_change# from v$datafile_header

FILE# STATUS REC FUZ CHECKPOINT_CHANGE#

1 ONLINE NO YES 1860869

2 ONLINE NO YES 1860869

3 ONLINE NO YES 1860869

4 ONLINE NO YES 1860869

5 ONLINE NO YES 1860869

6 ONLINE NO YES 1860869

7 ONLINE NO YES 1860869

8 ONLINE NO YES 1863020

9 ONLINE NO YES 1863020

9 rows selected.

SYS@seiang11g >

SYS@seiang11g > select file#,checkpoint_change#,online_change# from v$datafile

FILE# CHECKPOINT_CHANGE# ONLINE_CHANGE#

1 1860869 925702

2 1860869 925702

3 1860869 925702

4 1860869 925702

5 1860869 951158

6 1860869 0

7 1860869 0

8 1863020 1862119

9 1863020 1862119

Example 3: offline immediate in archive mode

First offline a data file in the tablespace, and then offline the corresponding tablespace, error ORA-01191 and ORA-01110 will occur.

SYS@seiang11g > alter database datafile'/ u01 offline

Database altered.

SYS@seiang11g >

SYS@seiang11g > alter tablespace wjqtest offline

Alter tablespace wjqtest offline

*

ERROR at line 1:

ORA-01191: file 8 is already offline-cannot do a normal offline

ORA-01110: data file 8:'/ u01qqtest01.dbf'

The offline immediate operation is used here.

SYS@seiang11g > alter tablespace wjqtest offline immediate

Tablespace altered.

SYS@seiang11g >

SYS@seiang11g > select file#, status, recover, fuzzy, checkpoint_change# from v$datafile_header

FILE# STATUS REC FUZ CHECKPOINT_CHANGE#

1 ONLINE NO YES 1863090

2 ONLINE NO YES 1863090

3 ONLINE NO YES 1863090

4 ONLINE NO YES 1863090

5 ONLINE NO YES 1863090

6 ONLINE NO YES 1863090

7 ONLINE NO YES 1863090

8 OFFLINE YES YES 1863090

9 OFFLINE YES YES 1863090

9 rows selected.

SYS@seiang11g >

SYS@seiang11g > select file#,checkpoint_change#,online_change# from v$datafile

FILE# CHECKPOINT_CHANGE# ONLINE_CHANGE#

1 1863090 925702

2 1863090 925702

3 1863090 925702

4 1863090 925702

5 1863090 951158

6 1863090 0

7 1863090 0

8 1863090 1862119

9 1863090 1862119

[oracle@seiang11g trace] $tail-f alert_seiang11g.log

Tue Sep 26 13:40:52 2017

Alter tablespace wjqtest offline immediate

Completed: alter tablespace wjqtest offline immediate

The similarity between immediate and temporary is that tablespaces can still perform Offline operations in the presence of "problematic" data files. But the difference is that Oracle will not perform check point unified SCN action on any data file in the case of the immediate parameter. This approach is similar to shutdown abort. Regardless of whether there is a problem with the file or not, Oracle does not check or unify the action.

One detail to note is the recover column in v$datafile_header. In the normal parameter, this column is not displayed, which means that the problem does not require attention and attention. In tempory mode, only those "problematic" files are marked as YES, that is, Recover is required. Other files with no problems are in the status of NO, that is, there is no need for recover. The above case proves this point.

In the case of the immediate parameter, all files are in the state of YES, which means that recover is required, for better or worse.

Let's try the online action.

SYS@seiang11g > alter tablespace wjqtest online

Alter tablespace wjqtest online

*

ERROR at line 1:

ORA-01113: file 8 needs media recovery

ORA-01110: data file 8:'/ u01qqtest01.dbf'

SYS@seiang11g >

SYS@seiang11g > recover datafile 8

Media recovery complete.

Still not, you need to recover all the files, simply recover the tablespace

SYS@seiang11g > alter tablespace wjqtest online

Alter tablespace wjqtest online

*

ERROR at line 1:

ORA-01113: file 9 needs media recovery

ORA-01110: data file 9:'/ u01qqtest02.dbf'

SYS@seiang11g > recover tablespace wjqtest

Media recovery complete.

[oracle@seiang11g trace] $tail-f alert_seiang11g.log

Tue Sep 26 13:42:44 2017

Checker run found 1 new persistent data failures

Tue Sep 26 13:43:04 2017

ALTER DATABASE RECOVER datafile 8

Media Recovery Start

Serial Media Recovery started

Recovery of Online Redo Log: Thread 1 Group 1 Seq 52 Reading mem 0

Mem# 0: / u01/app/oracle/oradata/OraDB11g/redo01.log

Media Recovery Complete (seiang11g)

Completed: ALTER DATABASE RECOVER datafile 8

Alter tablespace wjqtest online

ORA-1113 signalled during: alter tablespace wjqtest online...

Tue Sep 26 13:44:43 2017

ALTER DATABASE RECOVER tablespace wjqtest

Media Recovery Start

Serial Media Recovery started

Recovery of Online Redo Log: Thread 1 Group 1 Seq 52 Reading mem 0

Mem# 0: / u01/app/oracle/oradata/OraDB11g/redo01.log

Media Recovery Complete (seiang11g)

Completed: ALTER DATABASE RECOVER tablespace wjqtest

Summary

Let's summarize the three parameters of Offline.

(1) offline normal: it is the most commonly used parameter and the least prone to problems. When Offline Normal, Oracle will perform Check Point actions inside the tablespace to ensure that the SCN above each file header within the tablespace is consistent, that is, the data is consistent. If there is a situation in which the data file cannot be pushed forward to SCN, such as already Offline, offline normal failure reports an error.

(2) offline temporary: a shutdown mode that is slightly looser than Normal requirements. In Temporary mode, Oracle still "tries" to unify the SCN number of the file header inside the tablespace. If the data file can be unified, the Check Point action is performed, and if the file is not unified, the operation will not report an error, but its status will be marked as inconsistent. When the tablespace Online of Offline in Temporary mode, those inconsistent files with "problems" need to be media recovey. There is no problem, enter the check point data file, there is no need for recovery action.

(3) offline immediate: the loosest offline mode. In Immediate mode, Oracle does not perform check point actions, and regardless of whether there is a problem with Datafile, it will be set to require a Recover process. When re-online, the table space needs to be re-fully empty media recover.

Author: SEian.G (hard practice changes in 72, but it is difficult to laugh at 81)

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