Because Oracle Mediator is stateless, there is no performance overhead with pass through attachments. However, Oracle BPEL Process Manager dehydrates attachments and has performance overhead, even for pass through attachments. When using Oracle BPEL Process Manager for attachments over a period, the SOA Infrastructure schema can grow to its maximum size and encounter memory issues. It is recommended that you extend the database tablespace appropriately for the SOA Infrastructure schema to accommodate large attachments. Simultaneously, you can use purge scripts to purge completed instances along with the attachments table.

For information about purge scripts, see Administering Oracle SOA Suite and Oracle Business Process Management Suite.

For information about extending tablespaces, see Section "Extending Tablespaces to Avoid Problems at Runtime" of Administering Oracle SOA Suite and Oracle Business Process Management Suite.

In scenarios in which one BPEL process calls a second BPEL process within the same composite, the second BPEL process does not dehydrate the same attachment again.

In scenarios in which one BPEL process from composite 1 invokes a second BPEL process from composite 2 and optimization is disabled, composite 1 makes a SOAP call to composite 2. The second BPEL process does dehydrate attachments.