ORA-12899: Value too large for column "%s"."%s"."%s" (actual: %d, maximum: %d)

The value you are trying to insert into a column is too long.

eg:

SQL> create table test(n varchar2(1));

Table created.

SQL> insert into test values ('a');

1 row created.

SQL> insert into test values ('aa');
insert into test values ('aa')
                         *
ERROR at line 1:
ORA-12899: value too large for column "ME"."TEST"."N" (actual: 2, maximum: 1)

It can happen that the character you are trying to insert looks like there should be no problem:

SQL> desc test
 Name                                      Null?    Type
 ----------------------------------------- -------- -----------
 N                                                  VARCHAR2(1)

SQL> insert into test values ('?');
insert into test values ('?')
                         *
ERROR at line 1:
ORA-12899: value too large for column "ME"."TEST"."N" (actual: 3, maximum: 1)

This can happen due to the characterset the database is running in.

In a AL32UTF8 (unicode) database, some characters take more then 1 byte.

If you do not specify at create time what unit the size for a column is in, default it means the amount of bytes.

In our example, the ? will take 3 bytes due to the fact we are in a Unicode database and will cause the error.

SQL> select value from nls_database_parameters where parameter='NLS_CHARACTERSET';

VALUE
--------------------------------------------------------------------------------
AL32UTF8

We can fix this by telling that the size is in CHAR's instead of BYTE's:

SQL> alter table test modify(n varchar2(1 char));

Table altered.

SQL> desc test
 Name                                      Null?    Type
 ----------------------------------------- -------- -----------------
 N                                                  VARCHAR2(1 CHAR)

SQL> insert into test values ('?');

1 row created.