MAX_STRING

2.209 MAX_STRING_SIZE

MAX_STRING_SIZE controls the maximum size of VARCHAR2, NVARCHAR2, and RAW data types in SQL.

Property	Description
Parameter type	String
Syntax	`MAX_STRING_SIZE = { STANDARD \| EXTENDED }`
Default value	`STANDARD`
Modifiable	`ALTER SYSTEM` ... SID='*'^Foot 1
Modifiable in a PDB	Yes
Basic	No
Oracle RAC	Multiple instances must use the same value.

^Footnote 1

Use ALTER SYSTEM only when the database is in UPGRADE mode, and run the utl32k.sql script afterward, as explained in this section.

STANDARD means that the length limits for Oracle Database releases prior to Oracle Database 12c apply (for example, 4000 bytes for VARCHAR2 and NVARCHAR2, and 2000 bytes for RAW).

EXTENDED means that the 32767 byte limit introduced in Oracle Database 12c applies.

The COMPATIBLE initialization parameter must be set to 12.0.0.0 or higher to set MAX_STRING_SIZE = EXTENDED.

You can change the value of MAX_STRING_SIZE from STANDARD to EXTENDED. However, you cannot change the value of MAX_STRING_SIZE from EXTENDED to STANDARD.

By setting MAX_STRING_SIZE = EXTENDED, users are taking an explicit action that could introduce application incompatibility in their database. Applications that do not want to use the expanded data types can be rewritten for compatibility with either setting; for example, these applications could use explicit CASTs to fix the length of VARCHAR2 expressions during CREATE TABLE AS SELECT.

Altering MAX_STRING_SIZE will update database objects and possibly invalidate them, as follows:

Tables with virtual columns will be updated with new data type metadata for virtual columns of VARCHAR2(4000), 4000-byte NVARCHAR2, or RAW(2000) type.
- Functional indexes will become unusable if a change to their associated virtual columns causes the index key to exceed index key length limits. Attempts to rebuild such indexes will fail with ORA-01450: maximum key length exceeded.
Views will be invalidated if they contain VARCHAR2(4000), 4000-byte NVARCHAR2, or RAW(2000) typed expression columns.
Materialized views will be updated with new metadata VARCHAR2(4000), 4000-byte NVARCHAR2, and RAW(2000) typed expression columns

Increasing the Maximum Size of VARCHAR2, NVARCHAR2, and RAW Columns in a CDB

To increase the maximum size of VARCHAR2, NVARCHAR2, and RAW columns in a CDB and in all the PDBs in the CDB:

Connect to the CDB AS SYSDBA.
In the root, change the setting of MAX_STRING_SIZE to EXTENDED:
```
ALTER SESSION SET CONTAINER=CDB$ROOT;
ALTER SYSTEM SET max_string_size=extended SCOPE=SPFILE;
```
Note:

The root continues to use STANDARD semantics even after MAX_STRING_SIZE is set to EXTENDED. The reason for setting MAX_STRING_SIZE to EXTENDED in the root is so all the PDBs in the CDB can inherit the EXTENDED setting from the root.
Shut down the CDB.
Restart the CDB in UPGRADE mode.
```
startup upgrade;
```

Use the catcon.pl script to run the rdbms/admin/utl32k.sql script in the root and in all the PDBs in the CDB to increase the maximum size of the VARCHAR2, NVARCHAR2, and RAW columns. The --force_pdb_mode ‘UPGRADE’ option is used to ensure that all PDBs, including application root clones, are opened in migrate mode. Enter the SYS password when prompted:

$ cd $ORACLE_HOME/rdbms/admin
$ mkdir /scratch/mydir/utl32k_cdb_pdbs_output
$ $ORACLE_HOME/perl/bin/perl $ORACLE_HOME/rdbms/admin/catcon.pl -u SYS --force_pdb_mode 'UPGRADE' -d $ORACLE_HOME/rdbms/admin -l '/scratch/mydir/utl32k_cdb_pdbs_output' -b 
utl32k_cdb_pdbs_output utl32k.sql
catcon: ALL catcon-related output will be written to [/scratch/mydir/utl32k_cdb_pdbs_output/utl32k_cdb_pdbs_output_catcon_23172.lst]
catcon: See [/scratch/mydir/utl32k_cdb_pdbs_output/utl32k_cdb_pdbs_output*.log] files for output generated by scripts
catcon: See [/scratch/mydir/utl32k_cdb_pdbs_output/utl32k_cdb_pdbs_output_*.lst] files for spool files, if any
Enter Password: 
catcon.pl: completed successfully
$

Note:

The utl32k.sql script increases the maximum size of the VARCHAR2, NVARCHAR2, and RAW columns for the views where this is required. The script does not increase the maximum size of the VARCHAR2, NVARCHAR2, and RAW columns in some views because of the way the SQL for those views is written.

Connect to the CDB AS SYSDBA and shut down the database.
Restart the CDB in NORMAL mode.
```
startup;
```

Use the catcon.pl script to run the rdbms/admin/utlrp.sql script to recompile invalid objects in the root and in all the PDBs in the CDB. The --force_pdb_mode ‘READ WRITE’ option is used to ensure that all the PDBs (including application root clones) are opened in read write mode. Enter the SYS password when prompted:

$ cd $ORACLE_HOME/rdbms/admin
$ mkdir /scratch/mydir/utlrp_cdb_pdbs_output
$ $ORACLE_HOME/perl/bin/perl $ORACLE_HOME/rdbms/admin/catcon.pl -u SYS --force_pdb_mode 'READ WRITE' -d $ORACLE_HOME/rdbms/admin -l '/scratch/mydir/utlrp_cdb_pdbs_output' -b utlrp_cdb_pdbs_output utlrp.sql
catcon: ALL catcon-related output will be written to [/scratch/mydir/utlrp_cdb_pdbs_output/utlrp_cdb_pdbs_output_catcon_24271.lst]
catcon: See [/scratch/mydir/utlrp_cdb_pdbs_output/utlrp_cdb_pdbs_output*.log] files for output generated by scripts
catcon: See [/scratch/mydir/utlrp_cdb_pdbs_output/utlrp_cdb_pdbs_output_*.lst] files for spool files, if any
Enter Password: 
catcon.pl: completed successfully
$