How to query the relationship between Oracle table spaces and users

Oracle database is one of the commonly used relational databases. In order to better manage the database, we need to check the usage of table spaces, especially which user uses which table space. This article will introduce how to query the relationship between table spaces and users.

To query the relationship between table spaces and users, we need to first understand some basic concepts about Oracle table spaces and users.

Table space is a physical storage unit in Oracle database, used to store tables, indexes and other objects. Each database has at least one table space and multiple table spaces can be created. A user has a login ID and password in the database and can create and use objects such as tables, views, and stored procedures.

To query the usage of table space, you can use the following command:

SELECT tablespace_name, 
       sum(bytes/1024/1024) as "Total Size (MB)", 
       sum(decode(autoextensible,'YES',bytes/1024/1024,0)) as "AutoExtensible (MB)", 
       sum(decode(maxbytes,0,bytes,maxbytes)/1024/1024) as "MaxSize (MB)", 
       sum(decode(maxbytes,0,bytes,maxbytes)/1024/1024) - sum(bytes/1024/1024) as "Used (MB)", 
       round(((sum(decode(maxbytes,0,bytes,maxbytes)/1024/1024) - sum(bytes/1024/1024)) / sum(decode(maxbytes,0,bytes,maxbytes)/1024/1024)) * 100,2) || '%' as "Used %" 
FROM dba_data_files 
GROUP BY tablespace_name;

The above command will return the name, total size, automatic expansion size, maximum size, used size and usage rate of the table space, etc. information. Among them, dba_data_files is one of the system views in the Oracle database, used to view data file information.

In addition to checking the usage of table space, we can also query which user uses which table space. You can use the following command:

SELECT tablespace_name, 
       owner, 
       segment_name, 
       segment_type, 
       round(bytes/1024/1024,2) as "Size (MB)" 
FROM dba_segments 
WHERE owner = 'username' 
ORDER BY tablespace_name;

The above command will return the usage of the specified user (username) in each table space, including table space name, user name, object name, and object type As well as information such as the size of the occupied space. dba_segments is one of the system views in the Oracle database, used to view information about all objects in the database.

The above two commands can be combined through a joint query to query the usage of all users in each table space:

SELECT t.tablespace_name, 
       d.owner, 
       s.segment_name, 
       s.segment_type, 
       round(s.bytes/1024/1024,2) as "Size (MB)" 
FROM dba_data_files t, dba_segments s, dba_users d 
WHERE t.file_id = s.header_file AND t.tablespace_name = s.tablespace_name AND s.owner = d.username 
ORDER BY t.tablespace_name;

The above command will return all users in each table space Usage information, including table space name, user name, object name, object type, occupied space and other information.

In short, querying the relationship between table space and users is one of the important tasks of database management and optimization. By using the above commands and views, we can easily obtain information between database table spaces and users, which is beneficial to making good database management decisions.

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