Datatype Limits

A.1 Datatype Limits

This table documents the limits for datatypes, and includes comments about the datatypes.

Datatypes	Limit	Comments
`BFILE`	Maximum size: 2⁶⁴ bytes (18.44 exabytes) or OS file size limit, whichever is the lower value Maximum size of a file name: 255 characters Maximum size of a directory name: 128 bytes Maximum number of open BFILEs: see Comments	The maximum number of `BFILEs` is limited by the value of the `SESSION_MAX_OPEN_FILES` initialization parameter, which is itself limited by the maximum number of open files the operating system will allow.
`BLOB`	Maximum size: (4 GB - 1) * `DB_BLOCK_SIZE` initialization parameter (8 TB to 128 TB)	The number of LOB columns per table is limited only by the maximum number of columns per table (that is, 1000 if `MAX_COLUMNS` = `STANDARD` and 4096 if `MAX_COLUMNS` = `EXTENDED`^Foot 1). See Also: "MAX_COLUMNS" initialization parameter for additional details
`CHAR`	Maximum size: 2000 bytes	None
`CLOB`	Maximum size: (4 GB - 1) * `DB_BLOCK_SIZE` initialization parameter (8 TB to 128 TB)	The number of LOB columns per table is limited only by the maximum number of columns per table (that is, 1000 if `MAX_COLUMNS` = `STANDARD` and 4096 if `MAX_COLUMNS` = `EXTENDED`^Foot 1). See Also: "MAX_COLUMNS" initialization parameter for additional details
`JSON`	Maximum size: 32 MB	None
Literals (characters or numbers in SQL or PL/SQL)	Maximum size: 4000 characters	None
`LONG`^Foot 2	Maximum size: 2 GB - 1	Only one `LONG` column is allowed per table.
`NCHAR`	Maximum size: 2000 bytes	None
`NCLOB`	Maximum size: (4 GB - 1) * `DB_BLOCK_SIZE` initialization parameter (8 TB to 128 TB)	The number of LOB columns per table is limited only by the maximum number of columns per table (that is, 1000 if `MAX_COLUMNS` = `STANDARD` and 4096 if `MAX_COLUMNS` = `EXTENDED`^Foot 1). See Also: "MAX_COLUMNS" initialization parameter for additional details
`NUMBER`	999...(38 9's) x10¹²⁵ maximum value -999...(38 9's) x10¹²⁵ minimum value	Can be represented to full 38-digit precision (the mantissa) Can be represented to full 38-digit precision (the mantissa)
`NVARCHAR2`	Maximum size: 4000 bytes, or 32767 bytes if the `MAX_STRING_SIZE` initialization parameter is set to `EXTENDED` See Also: "MAX_STRING_SIZE" initialization parameter for additional details	None
Precision	38 significant digits	None
`RAW`	Maximum size: 2000 bytes, or 32767 bytes if the `MAX_STRING_SIZE` initialization parameter is set to `EXTENDED` See Also: "MAX_STRING_SIZE" initialization parameter for additional details	None
`VARCHAR2`	Maximum size: 4000 bytes, or 32767 bytes if the `MAX_STRING_SIZE` initialization parameter is set to `EXTENDED` See Also: "MAX_STRING_SIZE" initialization parameter for additional details	None

^Footnote 1

The absolute maximum number of columns in a table is 1000 or 4096, depending on the value of the MAX_COLUMNS initialization parameter. However, when you create an object table (or a relational table with columns of object, nested table, varray, or REF type), Oracle maps the columns of the user-defined types to relational columns, creating in effect hidden columns that count toward the maximum column limit. For details on how Oracle calculates the total number of columns in such a table, refer to Oracle Database Administrator’s Guide.

^Footnote 2

All forms of LONG data types (LONG, LONG RAW, LONG VARCHAR, LONG VARRAW) were deprecated in Oracle8i Release 8.1.6. For succeeding releases, the LONG data type was provided for backward compatibility with existing applications. In new applications developed with later releases, Oracle strongly recommends that you use the CLOB or NCLOB data type for storing large amounts of character data.