Selecting CLOB Across 21c Database Link Fails With "Clob Is Too Large to Be Stored in a Java String" (Doc ID 2907406.1)

Last updated on NOVEMBER 07, 2022

Applies to:

Symptoms

Given the following environment:

• Two 21c RDBMS instances connected using a database link
• Using any supported version of the Oracle JDBC driver

Executing a SQL SELECT statement that includes a LOB datatype across this dblink fails with the following exception:

Multiple conditions are necessary for the problem to reproduce.  If any of the following conditions are removed, then the problem no longer reproduces:

• The select statement must go through a database link
  
• The problem only happens if both databases in the database link are at version 21c; the problem does not reproduce if either database is version 19c or lower
  
• The select statement must include both non-null CLOB rows and null CLOB rows
• Over 1500 rows must have been selected before the problem appears
• The problem only happens when the SELECT statement contains the clause "order by <NUMBER COLUMN> asc" or contains no "order by" clause at all -- but if it's set to "order by <NUMBER COLUMN> desc", the problem goes away
• The application code calls the CLOB rows using getString() -- if getClob() is used instead, the problem goes away
   

Changes

Cause

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