Storage Requirements

By default, Oracle Database captures snapshots once every hour; the snapshot size varies depending on the database load. A typical system with an average of 10 concurrent active sessions may take anywhere from 1MB to 2MB per snapshot. Thus, the one hour default snapshot interval requires approximately 24MB to 48MB a day.

AWR data is stored in SYSAUX tablespace. The tablespace space required depends on the number of source databases. Using default settings with a typical load on source databases requires approximately 24MB to 48MB a day per source database.

To get a more accurate read on space requirements, run the awrinfo.sql script located in the ORACLE_HOME/rdbms/admin directory. In particular, see the "Size estimates for AWR snapshots" section, which contains "AWR size/day" and "AWR size/wk" values. On source databases, these values represent the average size of AWR data being generated on that database. On the AWR Warehouse database, these values represent the average size of AWR data imported from all the source databases. Use these values to estimate the warehouse space requirements. Naturally, as more source databases are added to the warehouse, the space required to store their AWR data increases.

Use Automatic Storage Management (ASM) with redundant disk groups and "Average Synchronous Single-Block Read Latency" of less than 40 milliseconds. The DBA_HIST_SYSMETRIC_SUMMARY view contains this and other metrics related to storage and I/O.

Additionally, ensure that there is enough free disk space (approximately 50GB) on the warehouse host to store the dump files containing incoming AWR data from source databases until the data can be loaded into the warehouse database.