Werk #19843: mk_oracle: avoid Oracle alert log parse errors on MOUNTED Data Guard standbys

Component	Checks & agents
Title	mk_oracle: avoid Oracle alert log parse errors on MOUNTED Data Guard standbys
Date	Apr 22, 2026
Level	Trivial Change
Class	Bug Fix
Compatibility	Compatible - no manual interaction needed
Checkmk versions & editions	2.6.0b1 Not yet released Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT 2.5.0p2 Not yet released Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT 2.4.0p27 Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT

On a standard Data Guard standby the database stays in MOUNTED mode, which means queries against non-fixed data-dictionary views (cdb_* / dba_*) cannot be parsed and Oracle raises ORA-01219 - database not open: queries allowed on fixed tables/views only.

The mk_oracle agent plugin issued such queries unconditionally for several sections, causing parse errors to accumulate in the Oracle alert log on every agent cycle even though the outer EXCEPTION handler swallowed the error for the agent output. Disabling sections via the "Sections - data to collect" ruleset was a global, all-or-nothing switch and therefore not a workable mitigation when only some monitored databases are standbys.

The following sections now consult v$database.open_mode before submitting their dynamic SQL, and run the query only when the database is open as a primary (READ WRITE) or as Active Data Guard (READ ONLY WITH APPLY):

• oracle_tablespaces
• oracle_ts_quotas
• oracle_jobs
• oracle_resumable
• oracle_locks (legacy query path)

Standard Data Guard standbys (MOUNTED) and plain read-only standbys (READ ONLY) no longer emit these queries and therefore no longer trigger ORA-01219 in the alert log. Behaviour on primaries and Active Data Guard instances is unchanged.

This affects both agents/plugins/mk_oracle (Linux/Unix) and agents/windows/plugins/mk_oracle.ps1 (Windows).

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