【YashanDB数据库】YashanDB如何回收表空间

确认表空间高水位线，是否有可回收空间。

select a.tablespace_name,a.high_water_mark,b.user_bytes,b.total_bytes from
(SELECT tablespace_name, max(header_block+blocks) * 8192 AS high_water_mark FROM dba_segments WHERE tablespace_name = 'USERS' GROUP BY tablespace_name) 
a,dba_tablespaces b
where a.tablespace_name=b.tablespace_name ;

如果total_bytes大于high_water_mark，代表有可回收的空间为total_bytes-high_water_mark，单位byte。

确认回收前，表空间磁盘大小

! ls -l $YASDB_DATA/dbfiles

回收空间

ALTER TABLESPACE USERS SHRINK SPACE KEEP 200M;

这里的200M需大于高水位线，不然无法回收。

确认回收后的表空间大小

select a.tablespace_name,a.high_water_mark,b.user_bytes,b.total_bytes from
(SELECT tablespace_name, max(header_block+blocks) * 8192 AS high_water_mark FROM dba_segments WHERE tablespace_name = 'USERS' GROUP BY tablespace_name) a,dba_tablespaces b
where a.tablespace_name=b.tablespace_name ;
 
! ls -l $YASDB_DATA/dbfiles