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When LOB update occurs, how to solve UNDO too large?

In the UPDATE process of LOB field,ORACLE does not use UNDO TABLESPACE space to store the pre-mirror space, but divides a space from the table space where the LOB field is located to make the mirror space. The size of this space is controlled by PCTVERSION parameter. The default value is 10, which means that 10% of the table space is divided as the mirror space.

PCTVERSION

This parameter specifies the percentage of all used BasicFiles LOB data space that can be occupied by old versions of BasicFiles LOB data pages. Under 11g compatibility, this parameter is ignored when SecureFiles LOBs are created.

This parameter specifies the percentage of all used BasicFiles LOB data space that older versions of BasicFiles LOB data pages can occupy. Under 11g compatibility, this parameter is ignored for SecureFiles LOB creation.

PCTVERSION Specifies the percentage of all used BasicFiles LOB data space that may be occupied by old versions of the LOB data pages. Not used for SecureFiles LOBs.

PCTVERSION specifies the percentage of all used BasicFiles LOB data space that may be occupied by older versions of LOB data pages. Not used for SecureFiles LOB.

In the following case, HR.ATLOG has LOB field, error message when EXPDP:

ORA-31693: Table data object "HR". "ATLOG" failed to load/unload and was skipped with the following error:

ORA-02354: Error exporting/importing data

ORA-01555: Snapshot is too old: Fallback segment number (name "") is too small

ORA-22924: Snapshots are too old

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