WRITEAPPEND|V4.2.1|OceanBase Database| docs|Distributed Database

WRITEAPPEND

Last Updated：2026-04-28 09:23:26 Updated

The WRITEAPPEND stored procedure appends a specified amount of data to the end of a specified internal LOB. The data to be written comes from the buffer parameter.

Applicability

This topic applies only to OceanBase Database Enterprise Edition. OceanBase Database Community Edition provides only the MySQL mode.

Syntax

DBMS_LOB.WRITEAPPEND (
lob_loc IN OUT NOCOPY BLOB,
amount  IN            INTEGER,
buffer  IN            RAW);

DBMS_LOB.WRITEAPPEND (
lob_loc IN OUT NOCOPY CLOB CHARACTER SET ANY_CS,
amount  IN            INTEGER,
buffer  IN            VARCHAR2 CHARACTER SET ANY_CS);

Parameters

Parameter	Description
lob_loc	The locator of the internal `LOB` to write to. For more information, see Considerations.
amount	The amount of data to write. The value is in bytes for `BLOBs`, and in characters for `CLOBs`.
buffer	The buffer for the write operation.

Note

If the amount specified is larger than the size of data in the buffer, an exception will be thrown. If the amount specified is smaller than the size of data in the buffer, only the data in the buffer will be appended to the LOB.

Exceptions

Exception	Description
VALUE_ERROR	Any of the `lob_loc`, `amount`, and `offset` parameters is `NULL`, invalid, or out of range.
INVALID_ARGVAL	Several possibilities: The value of the `amount` parameter is less than 1. The value of the `amount` parameter is greater than 32,767 bytes or its equivalent in characters.
QUERY_WRITE	Cannot perform a `LOB` write inside a query or PDML parallel execution server.
BUFFERING_ENABLED	The operation cannot be performed because `LOB` buffering is enabled.

Considerations

The form of the VARCHAR buffer must match the form of the CLOB parameter. If the type of the input LOB parameter is CLOB, the data in the buffer must be of the CHAR type.
When you call DBMS_LOB.WRITEAPPEND from the client, such as in a BEGIN or END block in OBClient, data in the buffer must use the client's character set. Before the data is written from the buffer to the LOB, the database converts the character set of the client's buffer to the character set of the server.
You can choose not to wrap the LOB operation inside the Open/Close API. If you did not open the LOB before the operation, the functional and domain indexes on the LOB column are updated during the call. However, if you opened the LOB before the operation, you must close it before you commit the transaction. When an internal LOB is closed, the functional and domain indexes on the LOB column are updated.
If you do not wrap the LOB operation in the Open/Close API, the functional and domain indexes are updated each time you write to the LOB. This may adversely affect performance. Therefore, we recommend that you wrap write operations on the LOB in the OPEN or CLOSE statement.
When necessary, WRITEAPPEND obtains the LOB before it appends data to it.

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