1.2.12 Fault Isolation with Quarantine
Oracle Exadata System Software has the ability to learn from the past events to avoid errors.
When a faulty SQL statement caused a crash of the server in the past, Oracle Exadata System Software quarantines the SQL statement so that when the faulty SQL statement occurs again, Oracle Exadata System Software does not allow the SQL statement to perform Smart Scan. This reduces the chance of server software crashes, and improves storage availability. The following types of quarantine are available:
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SQL Plan: Created when Oracle Exadata System Software crashes while performing Smart Scan for a SQL statement. As a result, the SQL Plan for the SQL statement is quarantined, and Smart Scan is disabled for the SQL plan.
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Disk Region: Created when Oracle Exadata System Software crashes while performing Smart Scan of a disk region. As a result, the 1 MB disk region being scanned is quarantined and Smart Scan is disabled for the disk region.
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Database: Created when Oracle Exadata System Software detects that a particular database causes instability to a cell. Instability detection is based on the number of SQL Plan Quarantines for a database. Smart Scan is disabled for the database.
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Cell Offload: Created when Oracle Exadata System Software detects some offload feature has caused instability to a cell. Instability detection is based on the number of Database Quarantines for a cell. Smart Scan is disabled for all databases.
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Intra-Database Plan: Created when Oracle Exadata System Software crashes while processing an intra-database resource plan. Consequently, the intra-database resource plan is quarantined and not enforced. Other intra-database resource plans in the same database are still enforced. Intra-database resource plans in other databases are not affected.
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Inter-Database Plan: Created when Oracle Exadata System Software crashes while processing an inter-database resource plan. Consequently, the inter-database resource plan is quarantined and not enforced. Other inter-database resource plans are still enforced.
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I/O Resource Management (IORM): Created when Oracle Exadata System Software crashes in the I/O processing code path. IORM is effectively disabled by setting the IORM objective to
basicand all resource plans are ignored. -
Cell-to-Cell Offload: See "Quarantine Manager Support for Cell-to-Cell Offload Operations".
When a quarantine is created, alerts notify administrators of what was quarantined, why the quarantine was created, when and how the quarantine can be dropped manually, and when the quarantine is dropped automatically. All quarantines are automatically removed when a cell is patched or upgraded.
CellCLI commands are used to manually manipulate quarantines. For instance, the administrator can manually create a quarantine, drop a quarantine, change attributes of a quarantine, and list quarantines.