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Don Burleson Blog 







max_string_size tips

Oracle Database Tips by Donald BurlesonJune 25, 2015


Question:  What does the max_string_size parameter do in Oracle 12c?

Answer:  In order to expand the maximum value of varchar2 (also nvarchar2 and raw) datatypes in Oracle 12c and beyond, the max_string_size parameter needs to be set to "extended".  This will change the maximum value from 4k (4096) to 32k (32767).

Oracle will now support varchar2(32767) and raw (32767) and nvarchar2(32767) (up from varchar2(4000). 

Less than 4K is stored inline in the data blocks, and more than 4K row lengths are stored out of line (BFILE)

To change max_string_size from the default of "standard" to "extended" you must bounce the database for the parameter to take effect and then run a utility to change all of the old maximum sizes for VARCHAR2 to the new larger values.

WARNING:  You MUST run utl32k.sql immediately after changing max_string_size=extended, else you risk invalidating the database columns.

1. Start Oracle in UPGRADE mode
3. Connect AS SYSDBA
4. Change the setting of MAX_STRING_SIZE to EXTENDED
5. Run $OH/rdbms/admin/utl32k.sql
6. Open the Oracle database.





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