ADR enhancements

• In oracle 12c the Automatic Diagnostic Repository contains a new log directory with 2 subdirectories :
  • DDL
  • Debug

The DDL log

• When you active the DDL logging in Oracle 12c using enable_ddl_logging=true, Oracle writes all DDL operations into the specific DDL log instead of writting it to the alert log.
• The DDL logging feature is part of the Oracle Change Management Pack.

The Debug Log

• The debug log contains unusual events which are not sufficiently critical to be recorded as incidents.
• This information is not destinated directly to the DBA and is mainly created to help the Oracle Support in case of problem.

Network-Related enhancements

• Oracle 12c introduces several network parameters used to optimize the network configuration.

Network Compression

• If you are licensed for the Advanced Compression Option, you can activate the network compression to reduce the network bandwidth used by your database.
• The advanced compression is setup using the following parameters:
  • SQLNET.COMPRESSION : can be set to ON or OFF depending if you want to activate the compression or no.
  • SQLNET.COMPRESSION_LEVELS : can be set to LOW or HIGH, the first one uses a low compression but consumes less CPU, the second uses the maximum compression but requires more CPU.
  • SQLNET.COMPRESSION_THRESHOLD: this parameter defines the minimum data size needed to trigger the compression.

SDU Size

•  The session data unit (SDU) is the size of data packets sent accross the network, when Oracle send data accross the network, it first compresses the data into buffers of the size of the SDU.
• In Oracle 12c you can set the DEFAULT_SDU_SIZE in the sqlnet.ora file. You should change the default SDU size only when your application average requested messages are greater than the default SDU (8KB)