text ORCL - Voir l'espace que l'on peux gagner en faisant un resize de DBF（avec generation

Posted 2021-04-29

set linesize 1000 pagesize 0 feedback off trimspool on
with
hwm as (
-- get highest block id from each datafiles ( from x$ktfbue as we don't need all joins from dba_extents )
select /*+ materialize */ ktfbuesegtsn ts#,ktfbuefno relative_fno,max(ktfbuebno+ktfbueblks-1) hwm_blocks
from sys.x$ktfbue group by ktfbuefno,ktfbuesegtsn
),
hwmts as (
-- join ts# with tablespace_name
select name tablespace_name,relative_fno,hwm_blocks
from hwm join v$tablespace using(ts#)
),
hwmdf as (
-- join with datafiles, put 5M minimum for datafiles with no extents
select file_name,nvl(hwm_blocks*(bytes/blocks),5*1024*1024) hwm_bytes,bytes,autoextensible,maxbytes
from hwmts right join dba_data_files using(tablespace_name,relative_fno)
)
select
case when autoextensible='YES' and maxbytes>=bytes
then -- we generate resize statements only if autoextensible can grow back to current size
'/* reclaim '||to_char(ceil((bytes-hwm_bytes)/1024/1024),999999)
||'M from '||to_char(ceil(bytes/1024/1024),999999)||'M */ '
||'alter database datafile '''||file_name||''' resize '||ceil(hwm_bytes/1024/1024)||'M;'
else -- generate only a comment when autoextensible is off
'/* reclaim '||to_char(ceil((bytes-hwm_bytes)/1024/1024),999999)
||'M from '||to_char(ceil(bytes/1024/1024),999999)
||'M after setting autoextensible maxsize higher than current size for file '
|| file_name||' */'
end SQL
from hwmdf
where
bytes-hwm_bytes>1024*1024 -- resize only if at least 1MB can be reclaimed
order by bytes-hwm_bytes desc
/