MAX_STRING_SIZE Parameter In Oracle 12c
This parameter was introduced in Oracle 12c. MAX_STRING_SIZE controls the maximum size of string size in Oracle database.Either we can set it to STANDARD or.EXTENDED The default value is STANDARD
MAX_STRING_SIZE = STANDARD means the maximum size of strings is 4000 bytes for VARCHAR2 and NVARCHAR2
MAX_STRING_SIZE = EXTENDED means maximum size can be upto 32767 byte .
We can change the value of MAX_STRING_SIZE from STANDARD to EXTENDED. But not from EXTENDED to STANDARD.
With MAX_STRING_SIZE set to STANDARD , if we try to set the length of column more than 4000, then it will throw ORA-00910 error.
SQL> SHOW PARAMETER MAX_STRING_
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
max_string_size string STANDARD
SQL>
SQL> create table UNIVERSITY ( COLLEGE_NAME VARCHAR2(8000));
create table UNIVERSITY ( COLLEGE_NAME VARCHAR2(8000))
*
ERROR at line 1:
ORA-00910: specified length too long for its datatype
STEPS for converting MAX_STRING_SIZE to EXTENDED:
1. Start database in upgrade mode:
SQL> SHUTDOWN IMMEDIATE;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL>STARTUP UPGRADE
ORACLE instance started.
Total System Global Area 1.4663E+10 bytes
Fixed Size 15697000 bytes
Variable Size 1.1878E+10 bytes
Database Buffers 2717908992 bytes
Redo Buffers 51404800 bytes
Database mounted.
Database opened.
2. Change the value to EXTENDED
SQL> alter system set MAX_STRING_SIZE='EXTENDED' SCOPE=BOTH;
System altered.
SQL> show parameter MAX_STRING_SIZE
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
max_string_size string EXTENDED
3.Run utl32k.sql script:
@?/rdbms/admin/utl32k.sql
SQL> @?/rdbms/admin/utl32k.sql
Session altered.
DOC>#######################################################################
DOC>#######################################################################
DOC> The following statement will cause an "ORA-01722: invalid number"
DOC> error if the database has not been opened for UPGRADE.
DOC>
DOC> Perform a "SHUTDOWN ABORT" and
DOC> restart using UPGRADE.
DOC>#######################################################################
DOC>#######################################################################
DOC>#
no rows selected
DOC>#######################################################################
DOC>#######################################################################
DOC> The following statement will cause an "ORA-01722: invalid number"
DOC> error if the database does not have compatible >= 12.0.0
DOC>
DOC> Set compatible >= 12.0.0 and retry.
DOC>#######################################################################
DOC>#######################################################################
DOC>#
PL/SQL procedure successfully completed.
Session altered.
1524 rows updated.
Commit complete.
System altered.
PL/SQL procedure successfully completed.
Commit complete.
System altered.
Session altered.
Session altered.
Table created.
Table created.
Table created.
Table truncated.
0 rows created.
PL/SQL procedure successfully completed.
no rows selected
DOC>#######################################################################
DOC>#######################################################################
DOC> The following statement will cause an "ORA-01722: invalid number"
DOC> error if we encountered an error while modifying a column to
DOC> account for data type length change as a result of enabling or
DOC> disabling 32k types.
DOC>
DOC> Contact Oracle support for assistance.
DOC>#######################################################################
DOC>#######################################################################
DOC>#
PL/SQL procedure successfully completed.
PL/SQL procedure successfully completed.
Commit complete.
4.Restart the database:
shutdown immediate;
startup
SQL> show parameter max_string
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
max_string_size string EXTENDED
Let’s create a table with length more than 4000.
SQL> create table UNIVERSITY ( COLLEGE_NAME VARCHAR2(8000));
Table created.
NOTE:- We don't have rollback option for this changes.
