11g Automatic Diagnostic Repository (ADR) Oracle 11g New Features Tips by Donald BurlesonJuly 13, 2015

Oracle 11g New Features Tips

New in Oracle 11g we see the new ADR (Automatic Diagnostic Repository) and Incident Packaging System, all designed to allow quick access to alert and diagnostic information.

The new $ADR_HOME directory is located by default at $ORACLE_BASE/diag, with the directories for each instance at $ORACLE_HOME/diag/$ORACLE_SID, at the same level as the traditional bdump, udump and cdump directories.

Starting in Oracle11g we no longer have many of the original OFA file system structures and we see that the ancient dump destination init.ora parameters (core_dump_dest,  background_dump_dest, user_dump_dest) are replaced by a single diagnostic_dest parameter, the place to go when Oracle wants to take a dump. 

You can use the new initialization parameter diagnostic_dest to specify an alternative location for the diag directory contents.

Automatic Memory Tuning

Prior to Oracle 11g, the DBA set the sga_target and sga_max_size parameters, allowing Oracle to reallocate RAM within the SGA.  The PGA was independent, as governed by the pga_aggregate_target parameter.

Now in Oracle 11g we see the memory_max_target parameter which governs the total maximum RAM for both the PGA and SGA regions and the new memory_target parameter which governs the existing sizes.  This allows RAM to be de-allocated from the SGA and transferred to the PGA.

This is an important Oracle11g new feature because it lays the foundation for inter-instance RAM memory sharing.

We are seeing the second age of mainframe computing, and server consolidation where it's not uncommon to find a dozen instances on a single large server.

As of Oracle 10g, Automatic Memory Management (AMM) only allows shifting of RAM within the confines of sga_max_size.  Now in Oracle 11g, we see this new Automatic Shared Memory Management (ASMM).  The memory_target parameter is dynamic (changeable with "alter system" commands), whereby RAM can be de-allocated from an instances SGA/PGA and re-allocated to another instance.

Conclusion

Oracle 11g's new performance tuning features allows a DBA to be much more proactive, while at the same time taking some of the 'busy work' from the DBA's day.  By gathering statistics that are more meaningful for Oracle's optimizer, Oracle is able to produce better results when data skewing is involved.  Automatic Memory Tuning enhances the previous Automatic Memory Management capabilities allowing full instance RAM tuning in a single parameter.  Testing can be more thoroughly accomplished for both reactive and proactive tuning with the SQL Performance Analyzer.  Finally, using the Automatic Diagnostic Repository maintenance, diagnostic alerts and messages can be managed in one centralized location.  While not specifically performance related, this feature allows the DBA to analyze diagnostic data quickly and effectively, freeing up time for performance analysis instead of chasing 'rabbit hole' issues.

NOTE: Rampant author Laurent Schneider has some additional insight into creating an Oracle Automatic Diagnostic Repository (ADR).