After migrating scanning from an 8.0 or earlier Protection Engine scanner to an 8.1 Protection Engine scanner using the Protection Engine SDK, scans are returning 500 internal server error. In the Protection engine logs, the files returning errors are logged with error "Decomposer 22".
The connector sending scan requests is sending the requests to the url icap://<SPE ip address or hostname>/avscan.
The older ICAP scanning method "avscan" has been deprecated and no longer functions correctly with version 8.1 and later.
Use one of the following methods to invoke antivirus scanning with Protection engine via ICAP: SYMCScanResp-AV or SYMCScanRespEx-AV.
For more details on the ICAP methods available and their usage and syntax, see Protection Engine for Cloud Services 8.1 Software Developer's Guide page 22 of the attached PDF, section About ICAP services