Extending undo tablespace

Question

Hi everyone!
I used this sql to check the status of my tablespaces.
SELECT /* + RULE */  df.tablespace_name "Tablespace",
       df.bytes / (1024 * 1024) "Size (MB)",
       SUM(fs.bytes) / (1024 * 1024) "Free (MB)",
       Nvl(Round(SUM(fs.bytes) * 100 / df.bytes),1) "% Free",
       Round((df.bytes - SUM(fs.bytes)) * 100 / df.bytes) "% Used"
  FROM dba_free_space fs,
       (SELECT tablespace_name,SUM(bytes) bytes
          FROM dba_data_files
         GROUP BY tablespace_name) df
WHERE fs.tablespace_name (+)  = df.tablespace_name
GROUP BY df.tablespace_name,df.bytes
UNION ALL
SELECT /* + RULE */ df.tablespace_name tspace,
       fs.bytes / (1024 * 1024),
       SUM(df.bytes_free) / (1024 * 1024),
       Nvl(Round((SUM(fs.bytes) - df.bytes_used) * 100 / fs.bytes), 1),
       Round((SUM(fs.bytes) - df.bytes_free) * 100 / fs.bytes)
  FROM dba_temp_files fs,
       (SELECT tablespace_name,bytes_free,bytes_used
          FROM v$temp_space_header
         GROUP BY tablespace_name,bytes_free,bytes_used) df
WHERE fs.tablespace_name (+)  = df.tablespace_name
GROUP BY df.tablespace_name,fs.bytes,df.bytes_free,df.bytes_used
ORDER BY 4 DESC;It shows that my undo tablespace has only 3% space left.
I just executed this SQL command but still the output is the same.
SQL> alter database datafile 'c:\ORACLE\DATA\PRODUCTION\DATAFILE\O1_MF_UNDO.DBF' autoextend on maxsize 50M;
Database altered.I mistakenly thought that the file's existing size is less than 50M.
But then realised the unused (3%) is 50M.
How should I increase the file's size now.
Please guide me.
Will the command I issued have a negative impact?
Thanks in advance.
Nith

Answer 1

user645399 wrote:
Hi everyone!
I used this sql to check the status of my tablespaces.
<snip>
It shows that my undo tablespace has only 3% space left.Which is not a problem of itself. Were you seeing an errors due to lack of space in the undo TS? Do you understand how the undo TS uses - and reuses - space?
>
I just executed this SQL command but still the output is the same.
SQL> alter database datafile 'c:\ORACLE\DATA\PRODUCTION\DATAFILE\O1_MF_UNDO.DBF' autoextend on maxsize 50M;
Database altered.
And of course the output is the same. Modifying the autoextend allocation of a file doesn't change the size of anything. It simply allows the file to grow if and when it becomes necessary. And with 3% still available, it is not necessary. And it won't become necessary until some DML causes that 3% to be exhausted.
I mistakenly thought that the file's existing size is less than 50M.
But then realised the unused (3%) is 50M.
How should I increase the file's size now.
Please guide me.
Will the command I issued have a negative impact?
Thanks in advance.
Nith