ORA-03137: malformed TTC packet from client rejected on 19c

 Problem:

An Application connecting to a 19.5 database is getting the following error intermittently:

In the Database alertlog the error looks like this:

ORA-03137: malformed TTC packet from client rejected: [3146] [4] [] [] [] [] [] []
ORA-03120: two-task conversion routine: integer overflow 

Analysis:

The application working fine but when it tries to insert a very big value into a CLOB column the DML will get interrupted throwing the above error.

Solution:

1- If the application's client/driver version is old, try to upgrade it to a newer version to be compatible with the database version on the server.

2- This error can also happen if the network is slow, or the packet between the client and server get interrupted for any reason, thus you may consider checking the network layer between the client and the server.

3- If you followed point 1 & 2, and you still keep getting this error, you may consider applying patch 31625618 if it's available for your DB version.