Dropping a table that uses hundreds of GBs does not free the disk size it uses immediately.
Is there any way to force Clickhouse to free the disk immediately?
Are you asking about database Atomic tables?
https://kb.altinity.com/engines/altinity-kb-atomic-database-engine/
database_atomic_delay_before_drop_table_sec=1
DROP TABLE t SYNC;
or SET database_atomic_wait_for_drop_and_detach_synchronously = 1
Related
On Oracle 12c, is the content of each datafile belonging to a single tablespace the same?
If yes, is it because of performance or backup purpose thus recommanding us to store each datafile on different drives?
If no then why would we create multiple datafiles for a single tablespace when we can autoextend each datafile?
No.
The idea of multiple datafiles supporting a single tablespaces is to be able to use striping. This ofcourse only makes sense if your server has multiple physical storage devices that preferably also have their own io interface.
À table will be in the tablespaces and can allocate space in all available datafiles. So the table data can be in all datafiles.
If your io system does not consist of multiple physical devices you might as well use a bigfile tablespace that just has one big datafile. In older releases this was a restore nightmare because the backup and restore was performed file by file.
We are using a one-time merge query in oracle 12c which fetches around "22633334" records of data and updates it in the target table, but every time when the query run's it throws "ORA-01652: unable to extend temp segment by 64 in tablespace TEMP" issue, the DBA has already extended it to 60 GB. Can anyone tell me how this can be resolved or what would be the ideal temp space to be allocated for this volume of data?
Oracle uses that space to build temporary result sets and perform sorts. The amount of space required depends on the precise explain plain of your query (check it out and it should give you some clues), but could be several times the actual amount of data in the tables if there are joins. The number of records matters not at all; it's about the size of the records and what Oracle is trying to do with them. You want to avoid full table scans, unnecessary sorts, and that sort of thing. Make sure your table statistics are up to date. In the end, it needs what it needs and all you can do is increase your TEMP tablespace size until it works.
I have a friend who has a website and asked me for help.
I often use MySQL databases but never Oracle databases.
And unfortunately he has an Oracle database, so I can't find a solution.
The available disk space is slowly decreasing... I delete a lot of lines from the table but that doesn't solve his problem.
The database continues to take up disk space slowly.
I read that LOB files do not return disk space, even if you delete data.
How can I reorganize LOB files easily with a simple request?
(or/and) How can I recover disk space on Oracle?
SELECT DISTINCT VERSION FROM PRODUCT_COMPONENT_VERSION
12.1.0.1.0
The BLOB column exists within the table blocks along with data even after deletion. It is only marked as unused. You can use the following command to free up space from the BLOB table:
ALTER TABLE <YOUR_TABLE_NAME> MODIFY
LOB <LOB_COLUMN_NAME>
( SHRINK SPACE );
Now, Table must have released some space and it is now available to be used within the tablespace.
Further, you can just alter the data file and reduce the size of the data file accordingly to free up space from Disk. (Note: Space allocated to the data file will not be automatically reduced. It must be done manually)
Cheers!!
I want more file system space. so I truncate all tables in oracle ,but the higher water mark still so high, I shrink my tables; I had google it ,shrink only cut dowen the space higher than hwm It reduce some space, but It help less.and I find that tablespace is only used 1% space.how can I free the space in my file system.
Finally, We find that we get a droped table in the end of the segment, so the hwm is high, we purge the tablespace , then alter table datefile resize.
One way to do it is to export the database at user level using exp. Then drop and recreate the user. Then do an import. This should free up some space.
You can also use alter database datafile to reduce one of your datafiles (these are the physical files on your hard drive used by the db).
There is a great overview of how to reclaim datafile space in this article. TL DR - export, drop user, alter datafile, import.
http://oracle-base.com/articles/misc/reclaiming-unused-space.php
My boss has a concern that creating LOB columns in our database tables could result in effectively permanent storage overhead if we do not partition the table and drop the partitions over time (as opposed to just deleting the records). He thinks that data for the LOB will be stored separately when the record is created, which seems to be correct, but that Oracle may not delete the data for the LOB column when the row is deleted.
Is this correct or even possible? I find it hard to believe that the DBMS would handle object storage so poorly. We are using Oracle 11g if that changes anything.
I eventually found this ask tom question which covers the same topic.
When the database creates an extent to store the LOBs it is associated directly with the table. When rows containing those LOBs are deleted, the LOBs are removed from the extent which remaining the same size (it does not shrink just because a LOB was removed). However, the table is able to reuse the space from the removed LOB as one would expect.
So while the database at large is not able to reuse the free space in an extent created for a table's LOB storage, the space IS free for use by the table. The extent will exist (and therefore take up space that would otherwise be completely available to the database) until table is dropped or truncated, or the extent is explictly deallocated.
In the end, unless the extent(s) remaining allocated to the table is a concern (or there are other concerns that may be addressed through partition), creating partitions solely for this purpose is unnecessary.