I create a sbspace and create a table with blob column。 
blob column in sbspace。
insert many many rows.

dbaccess dbname -
> truncate table tabname;

$ onstat -d 

I find  sbspace's  remain unchanged。

how can I free sbspace ？

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David Cui
Technical support
gbase.cn
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#Informix

There are two lines for each sbspace chunk in onstat -d:

• User Data (sblobs)
• Metadata (sblob headers) - you can think of those as regular tables (partitions), only not directly accessible

First one would reflect your truncate immediately, showing all your sblobs' space being released ('free' going up).
Second one's used space (size - free) will never shrink, that's just how partitions work. Yet that doesn't mean that the space previously occupied by your sblobs's headers hadn't been freed and wouldn't be available for and reused by any new sblobs's headers.
Quite typically Metadata consumption is only a fraction of the space reserved for or occupied by User Data anyway.

HTH

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Andreas Legner
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Thanks Andreas 

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ZhiWei Cui
GBASE
ShiJiaZhuang
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Original Message:
Sent: Fri October 29, 2021 10:26 AM
From: Andreas Legner
Subject: how to from informix sbspace

There are two lines for each sbspace chunk in onstat -d:

• User Data (sblobs)
• Metadata (sblob headers) - you can think of those as regular tables (partitions), only not directly accessible

First one would reflect your truncate immediately, showing all your sblobs' space being released ('free' going up).
Second one's used space (size - free) will never shrink, that's just how partitions work. Yet that doesn't mean that the space previously occupied by your sblobs's headers hadn't been freed and wouldn't be available for and reused by any new sblobs's headers.
Quite typically Metadata consumption is only a fraction of the space reserved for or occupied by User Data anyway.

HTH

------------------------------
Andreas Legner
------------------------------