|Managing LOB size
|Use LOB commands to adjust the storage size of LOBs
DBMS_LOB built-in PL/SQL package. A number of procedures in this package help you adjust the way that LOBs are stored, but four of them of them are most commonly used, as shown in the following table:
DBMS_LOB.COPY( dest_lob, src_lob dest_offset, src_offset, amt);
where dest_lob is the LOB locator to which the data in src_lob is to be copied to, src_lob is the LOB locator of thesource LOB, dest_offset is the offset from the beginning of the destination LOB, src_offset is the offset from the beginningof the source LOB, and amt is the amount of bytes to be copied.
|You can also specify an offset to begin copying the data from src_lob, the number of bytes to be copied, and the offset for thecopied data to be placed at in dest_lob.
DBMS_LOB.APPEND( dest_lob, src_lob);where dest_lob is the LOB locator that the data in the src_lob is to be appended to and src_lob is the LOB locator or the source LOB.
|This procedure will take the contents from one LOB and append them to the end of another LOB.
DBMS_LOB.TRIM( lob_locator, newlen);
where lob_locator is the LOB locator for the LOB and newlen is an integer representing the new number of bytes in the LOB.
|You must first retrieve the locator for the LOB. newlen cannot be more than the existing length of the LOB or an exception will be returned.
DBMS_LOB.ERASE( lob_loc, amount, offset);
where lob_loc is the LOB locator for the target LOB, amount is an integer representing the number of bytes to be erased, andoffset is an integer representing the offset of the action.
|You can erase data from within a LOB by setting an offset and a number of characters. The size of the LOB is not reduced when the
ERASE() procedure is used.