DBCollect/Why

Why DBCollect

Question: Why can't we just send some AWR reports?

AWR reports are great but have a few problems and limitations for our purpose:

• We need AWR reports with a consistent format (HTML, single instance, correct timezone) and over a long period (default 10 days, with a standard 1-hour interval this results in about 240 AWR reports per database instance)
• We need the AWRs for each database instance. DBCollect detects all instances automagically (in most cases). The alternative is to manually start SQL*Plus for each instance and generate all reports
• AWR only provides performance and limited configuration metrics. There is no database size/config information such as sizes of tablespaces, redo logs, temp files, segments, ASM disks/diskgroups, archive/flashback/bct files. DBCollect runs additional (SELECT) queries to get this additional database information
• No OS configuration or hardware information (such as CPU type & model, memory, etc)
• No disk/network configuration
• No UNIX SAR/sysstat performance data
• No compression, backup, archiving details
• AWRs are sometimes generated using non-English locale (cannot be parsed)
• AWRs are sometimes generated in txt format instead of html (hard to parse, error-prone)
• AWRs are sometimes provided as RAC versions (completely different layout, hard to parse)
• Usually only a few AWRs are provided, sometimes with a very large interval (many hours or even days) which is not detailed enough to do accurate sizings or performance analysis
• No way to know if there are other instances on the same system for which we need to know details

Security / Stability considerations

• dbcollect does not modify database or OS data/files (except temporary files) and uses only SELECT statements
• It can be run as UNIX nobody and with a database read-only user (DBSNMP)
• There is some performance overhead for generating AWR reports - this can be managed using the --tasks option.
• No network connections are initiated. The workload data is stored on the host itself, in /tmp.

For more information, see DBCollect/Considerations