Data Guard – update

In March, Oracle MAA has published a white paper for implementing Data Guard on Exadata platforms. (

Although the paper is focused on Exadata, some information can be applied to non-Exadata systems as well:

  • Corruption Protection:
    • Primary:
    • (Physical) Standby:
  • Network Tuning:
    TCP Send/Receive Buffers: 3 x Bandwith Delay Product or 10 MB, whichever is greater
  • Redo Transport Modes:
    • SYNC is recommended if round-trip-time is less than 5 ms.  Impact of SYNC Mode on primary performance has been improved because local online redo log write and redo shipping is not done sequentially anymore but in parallel.
    • ASYNC: Transport Lag is reduced because Redo is not read from online redo log from disk but from log buffer if possible. init.ora log_buffer might need to be increased for this to yield the maximum benefit.
  • LOGGING/NOLOGGING: Normally, in Data Guard you set database-wide “ALTER DATABASE FORCE LOGGING”. In Data Warehouse environments, it might be advisable to set it to NOLOGGING and decide on a tablespace-basis whether the tablespace should allow or disallow NOLOGGING operations. E.g. a tablespace containing only transient, recreatable  or non-critical data might benefit from being set to NOLOGGING for certain bulk operations. (CTAS, Direct Path Inserts, index rebuilds, etc.)
  • STANDBY-FIRST Patches: Some patches (PSU, CPU, PSE) will be flagged in the patch README with “Standby-First”. This means that they can be applied on a physical standby before being applied on the primary. For regular patches, this was not supported.

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