SOLUTION
- To check the current size of the Undo tablespace:
select sum(a.bytes) as undo_size from vdatafile a, vtablespace b, dba_tablespaces c where c.contents = 'UNDO' and c.status = 'ONLINE' and b.name = c.tablespace_name and a.ts# = b.ts#;
- To check the free space (unallocated) space within Undo tablespace:
select sum(bytes)/1024/1024 "mb" from dba_free_space where tablespace_name ='<undo tablespace name>';
3.To Check the space available within the allocated Undo tablespace:
select tablespace_name , sum(blocks)*8/(1024) reusable_space from dba_undo_extents where status='EXPIRED' group by tablespace_name;
- To Check the space allocated in the Undo tablespace:
select tablespace_name, sum(blocks) * 8 / (1024) space_in_use
from dba_undo_extents
where status IN ('ACTIVE', 'UNEXPIRED')
group by tablespace_name;
Alternatively, below one SQL can be used as well:
with free_sz as
(select tablespace_name, sum(f.bytes) / 1048576 / 1024 free_gb
from dba_free_space f
group by tablespace_name),
a as
(select tablespace_name,
sum(case
when status = 'EXPIRED' then
blocks
end) * 8 / 1048576 reusable_space_gb,
sum(case
when status in ('ACTIVE', 'UNEXPIRED') then
blocks
end) * 8 / 1048576 allocated_gb
from dba_undo_extents
where status in ('ACTIVE', 'EXPIRED', 'UNEXPIRED')
group by tablespace_name),
undo_sz as
(select tablespace_name, df.user_bytes / 1048576 / 1024 user_sz_gb
from dba_tablespaces ts
join dba_data_files df
using (tablespace_name)
where ts.contents = 'UNDO'
and ts.status = 'ONLINE')
select tablespace_name,
user_sz_gb,
free_gb,
reusable_space_gb,
allocated_gb,
free_gb + reusable_space_gb + allocated_gb total
from undo_sz
join free_sz
using (tablespace_name)
join a
using (tablespace_name);
GOAL
Sometimes customer need to check the undo tablespace usage history, by using crontab and Linux shell script, we can give customer flexible ability to check undo tablespace usage information, or other dictionary view information. I am giving an example to show the method. This has been tested in Oracle Enterprise Linux 6.5 and bash shell. If using other kind of OS or shell, the script might need to be changed accordingly.
Disclaimer:
NOTE: In the images and/or the document content below, the user information and environment data used represents fictitious data from the Oracle sample schema(s), Public Documentation delivered with an Oracle database product or other training material. Any similarity to actual environments, actual persons, living or dead, is purely coincidental and not intended in any manner.
SOLUTION
Step 1. Edit shell script to set oracle database related environment variables.
$ vi <PATH_To_Your_Script_Directory>/SetEnv.sh
$ cat <PATH_To_Your_Script_Directory>/SetEnv.sh
#!/bin/bash
export ORACLE_HOME=<PATH_To_DB_HOME>
export ORACLE_BASE=<PATH_To_ORACLE_BASE>
export ORACLE_SID=<oracle sid>
export PATH=PATH:ORACLE_HOME/bin
$
Grant running permission:
$ chmod u+x <PATH_To_Your_Script_Directory>/SetEnv.sh
Step 2. Edit shell script to run sql.
$ vi <PATH_To_Your_Script_Directory>/CheckUndo.sh
In this shell script, we run the ". <PATH_To_Your_Script_Directory>/SetEnv.sh" to set environment variable.
$ cat <PATH_To_Your_Script_Directory>/CheckUndo.sh
#!/bin/bash
. <PATH_To_Your_Script_Directory>/SetEnv.sh
sqlplus -s sys/oracle 'as sysdba' <<EOF
spool <PATH_To_Your_Script_Directory>/CheckUndo.txt APPEND
set linesize 200
col tablespace_name for a20
select to_char(sysdate,'yyyymmdd hh24:mi:ss') date_time from dual;
-- <Your sql statement for undo tablespace usage querying>
-- OR
with free_sz as ( select tablespace_name, sum(f.bytes)/1048576/1024 free_gb from dba_free_space f group by tablespace_name ) , a as ( select tablespace_name , sum(case when status = 'EXPIRED' then blocks end)*8/1048576 reusable_space_gb , sum(case when status in ('ACTIVE', 'UNEXPIRED') then blocks end)*8/1048576 allocated_gb from dba_undo_extents where status in ('ACTIVE', 'EXPIRED', 'UNEXPIRED') group by tablespace_name ) , undo_sz as ( select tablespace_name, df.user_bytes/1048576/1024 user_sz_gb from dba_tablespaces ts join dba_data_files df using (tablespace_name) where ts.contents = 'UNDO' and ts.status = 'ONLINE' ) select tablespace_name, user_sz_gb, free_gb, reusable_space_gb, allocated_gb , free_gb + reusable_space_gb + allocated_gb total from undo_sz join free_sz using (tablespace_name) join a using (tablespace_name);
EOF
$
Grant running permission:
$ chmod u+x <PATH_To_Your_Script_Directory>/CheckUndo.sh
Step 3. Running the shell script manually to check to effect.
$ <PATH_To_Your_Script_Directory>/CheckUndo.sh
DATE_TIME
20240204 02:42:17
TABLESPACE_NAME USER_SZ_GB FREE_GB REUSABLE_SPACE_GB ALLOCATED_GB TOTAL
UNDOTBS1 .331054688 .314208984 .007080078 .009765625 .331054688
$
The result example looks like the following:
$ cat <PATH_To_Your_Script_Directory>/CheckUndo.txt
DATE_TIME
20240204 02:43:01
TABLESPACE_NAME USER_SZ_GB FREE_GB REUSABLE_SPACE_GB ALLOCATED_GB TOTAL
UNDOTBS1 .331054688 .314208984 .007080078 .009765625 .331054688
$
Step4. Make crontab setting, and check the effect.
Run as oracle user, to edit crontab setting:
For example, if we want to run the above shell script every 1 minute:
$ crontab -e
At the editing window, add the following line
* * * * * <PATH_To_Your_Script_Directory>/CheckUndo.sh
After saving it (similar to using vi), check the contents by:
$ crontab -l
* * * * * <PATH_To_Your_Script_Directory>/CheckUndo.sh
$
Step 5. Check the automatic running effect.
$ rm -f <PATH_To_Your_Script_Directory>/CheckUndo.txt
Wait for a few minutes, and then check:
$ cat <PATH_To_Your_Script_Directory>/CheckUndo.txt
DATE_TIME
20240204 02:44:01
TABLESPACE_NAME USER_SZ_GB FREE_GB REUSABLE_SPACE_GB ALLOCATED_GB TOTAL
UNDOTBS1 .331054688 .314208984 .007080078 .009765625 .331054688
DATE_TIME
20240204 02:45:02
TABLESPACE_NAME USER_SZ_GB FREE_GB REUSABLE_SPACE_GB ALLOCATED_GB TOTAL
UNDOTBS1 .331054688 .314208984 .007080078 .009765625 .331054688
$
We can see that the undo tablespace usage is recorded every 1 minute.
If we want that script to run every 10 minutes, we can change the content to:
10 * * * * <PATH_To_Your_Script_Directory>/CheckUndo.sh
If we cannot edit crontab as oracle user, we can edit via root user, and change the content to:
10 * * * * su - oracle -c <PATH_To_Your_Script_Directory>/CheckUndo.sh
The crontab setting varies depends on OS type and version, please confirm detail with OS vendor.
Please notice:
In this example the size of <PATH_To_Your_Script_Directory>/CheckUndo.txt grows along the time, so please check the size periodically, if it is too big, please move it to other location, and delete the original contents(eg: truncate --size 0 <PATH_To_Your_Script_Directory>/CheckUndo.txt).