Why is the value of bytes larger than that of maxbytes
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Objective:
This article explains why the value of bytes in DBA_DATA_FILES is larger than the value of maxbytes.
Description:
When a datafile manually resize to a value greater than maxsize (maxbytes), the value of bytes in DBA_DATA_FILES is larger than the value of maxbytes
When the datafile is set to autoextend on, the maxbytes value in dba_data_files is automatically settled to a non-zero value.
The bytes in dba_data_files is the current size of the datafile (in bytes)
Here is an example:
Explanation:
When datafile is resize, the maxbytes value in dba_data_files is not updated, and the column that is updated is only the bytes column.
The maxbytes value in dba_data_files is updated only when ALTER DATABASE command with MAXSIZE option is used.
Step-1: Create a New Tablespace
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SQL > create tablespace tst datafile'/ u01 size autoextend on
Tablespace created.
SQL > col file_name for A60
SQL > set lines 200
SQL > select file_name, bytes, maxbytes, autoextensible from dba_data_files
FILE_NAME BYTES MAXBYTES AUT
/ u01/app/oracle/oradata/DBdb/users01.dbf 3207331840 3.4360E+10 YES
/ u01/app/oracle/oradata/DBdb/undotbs01.dbf 2710568960 3.4360E+10 YES
/ u01/app/oracle/oradata/DBdb/sysaux01.dbf 744488960 3.4360E+10 YES
/ u01/app/oracle/oradata/DBdb/system01.dbf 2936012800 3.4360E+10 YES
/ u01/app/oracle/oradata/DBdb/example01.dbf 355205120 3.4360E+10 YES
/ u01/app/oracle/fast_recovery_area/DBDB/newback/ts_xxf_01.dbf 10485760 0 NO
/ u01/app/oracle/oradata/DBdb/tst.dbf 5242880 3.4360E+10 YES
7 rows selected.
Step-2: Alter the MAXSIZE value from default value
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SQL > alter database datafile'/ u01 autoextend on maxsize
Database altered.
SQL > select file_name, bytes, maxbytes, autoextensible from dba_data_files
FILE_NAME BYTES MAXBYTES AUT
/ u01/app/oracle/oradata/DBdb/users01.dbf 3207331840 3.4360E+10 YES
/ u01/app/oracle/oradata/DBdb/undotbs01.dbf 2710568960 3.4360E+10 YES
/ u01/app/oracle/oradata/DBdb/sysaux01.dbf 744488960 3.4360E+10 YES
/ u01/app/oracle/oradata/DBdb/system01.dbf 2936012800 3.4360E+10 YES
/ u01/app/oracle/oradata/DBdb/example01.dbf 355205120 3.4360E+10 YES
/ u01/app/oracle/fast_recovery_area/DBDB/newback/ts_xxf_01.dbf 10485760 0 NO
/ u01/app/oracle/oradata/DBdb/tst.dbf 5242880 10485760 YES
7 rows selected.
Step-3: Resize the datafile to a value higher than MAXBYTES
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SQL > alter database datafile'/ u01 resize
Database altered.
SQL > select file_name, bytes, maxbytes, autoextensible from dba_data_files
FILE_NAME BYTES MAXBYTES AUT
/ u01/app/oracle/oradata/DBdb/users01.dbf 3207331840 3.4360E+10 YES
/ u01/app/oracle/oradata/DBdb/undotbs01.dbf 2710568960 3.4360E+10 YES
/ u01/app/oracle/oradata/DBdb/sysaux01.dbf 744488960 3.4360E+10 YES
/ u01/app/oracle/oradata/DBdb/system01.dbf 2936012800 3.4360E+10 YES
/ u01/app/oracle/oradata/DBdb/example01.dbf 355205120 3.4360E+10 YES
/ u01/app/oracle/fast_recovery_area/DBDB/newback/ts_xxf_01.dbf 10485760 0 NO
/ u01/app/oracle/oradata/DBdb/tst.dbf 20971520 10485760 YES
7 rows selected.
SQL >
The maximum size that a tablespace tst (/ u01/app/oracle/oradata/DBdb/tst.dbf) can reach is the value of dba_data_files.bytes.
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