Oracle shrink tablespace high water mark Oct 1, 2016 · In Oracle 10g onwards you can also use the shrink command to re-organize the data. I recently dropped some schemas on a tablespace and I know there are lot space in the datafiles below the high water mark. May 18, 2001 · High Water Mark Hello Tom,I have gone through with Oracle documentation and some of your article and question/Answer about High Water Mark. Compacting the segment requires row movement. Example of use in PL/SQL Oct 15, 2007 · If you envision a table, for example, as a 'flat' structure or as a series of blocks laid one after the other in a line from left to right, the high-water mark (HWM) would be the rightmost block that ever contained data, as illustrated in Figure 10-1. This is supported by OEM, which tells me Aug 3, 2021 · Oracle cannot shrink the datafile below the high watermark and if you attempt to shrink the file below that high watermark you’ll get ORA-03297. I am kind of confuced with HWM. You can complete deallocate space with: truncate table May 22, 2025 · Oracle Database Backup Service - Version N/A and later: Optimizing Database disk space using Alter table shrink space/move compress Oct 26, 2014 · By default, Oracle Database compacts the segment, adjusts the high water mark, and releases the recuperated space immediately. Oct 19, 2018 · Database Administration (MOSC) Shrink Sysaux Tablespace High Watermark blocked not by Table and Index Oct 19, 2018 1:58PM edited Jun 7, 2019 3:52PM 17 comments Answered. Before using this command, you should have row movement enabled. Aug 23, 2000 · Shrinking High Water Mark I have noticed that the HWM will only go down if the table is truncated. According to my knowledge, 'all Oracle segments have an upper boundary containing the data within the segment. When these segments grow, the high water mark moves FROM dba_segments ORDER BY 5 DESC) WHERE ROWNUM <= 20; To reclaim unused space from a table segment, first enable row movement ALTER TABLE hr. Apr 24, 2024 · Shrinking and compacting fragmented free space on Oracle tables and high water mark HWM. Oct 15, 2007 · If you envision a table, for example, as a 'flat' structure or as a series of blocks laid one after the other in a line from left to right, the high-water mark (HWM) would be the rightmost block that ever contained data, as illustrated in Figure 10-1. 2 on Redhat linux. +---- high water mark of newly created table | V Apr 10, 2010 · I have Oracle 11. Jan 27, 2018 · The ALTER TABLE SHRINK SPACE command is used to perform online segment shrinks for tables, LOBs and IOT overflow segments. This command is only applicable for the tables whose tablespace defined with auto segment space management. employees ENABLE ROW MOVEMENT; Recover the unused space and reset the high water mark (HWM) ALTER TABLE hr. Jan 21, 2025 · Understanding and Resolving High water mark issues in Oracle database 19c, This is the crucial part of the oracle database. Sep 14, 2000 · The high water mark of a file in a tablespace has no bearing on performance whatsoever. employees SHRINK SPACE CASCADE; Dec 12, 2022 · Quick reference for database operation support ! Resizing datafiles and understanding the High Water Mark Resizing datafiles is something that I seem to do a lot of. This upper boundary is ca Jul 16, 2020 · You've done some thorough analysis of one table there! But what other tables are there in that tablespace? If you have some tiny table with extents allocated after the huge table, you're still unable to shrink the data file! PS - truncate resets the high water mark for the table, and by default deallocates all space above the minextents. Table High water marks and Full Table Scans When we create an Oracle table we must specify a STORAGE clause. This storage clause determines the initial and next extent sizes, and Oracle allocates data blocks within the tablespace based upon the values for these parameters. SQL> alter table DEMO enable row movement; Table altered. Usually, I am increasing them to allow for data growth but sometimes I need to shrink them to reclaim unused space. The above does not indicate any problems to me unless you are short on space in the filesystem in which case the above shows how small you could shrink the files to. If I do the following will it lower the HWM:CREATE TABLE temp AS SELECT * FROM table_name;TRUNCATE table_name;INSERT INTO table_name SELECT * FROM temp;COMMIT;This has been successful at times in lowering t Aug 28, 2025 · Why Tablespace Bloat Happens In Oracle databases, segments such as tables, indexes, and LOBs consume extents that are allocated in datafiles. Sep 24, 2025 · This article explains, with examples, how to view the high water mark and when the high water mark is reset. The queries given in this article applies when the segment , whose high water mark has to be determined, is in one datafile and is not spawned across multiple datafiles. scnyh zqclty yxguz qsowjuq ptqnps vkd mlmdj hyz jsckv vhbkr tytu imnsn zfcpcoc xnh lcxm