9 True Cache

This chapter provides information about the Oracle True Cache metrics.

True Cache is an in-memory, consistent, and automatically managed SQL and key-value (object or JSON) cache for Oracle Database. For information on True Cache, see Overview of Oracle True Cache in Oracle True Cache User's Guide.

Note:

True Cache metrics in Oracle Enterprise Manager are currently available for True Cache CDB targets.

Database Load

This section provides information on the metrics in the Database Load category, which monitor resource usage and load.

Target Version Evaluation and Collection Frequency
23ai and later Every 15 minutes
Metric Name Description
Average Active Sessions The number of average active sessions, which includes sessions that are either working or waiting.
CPU Count The number of CPUs available for the database.
CPU Time (seconds) The average rate of accumulation of CPU time by foreground sessions.
CPU Utilization (%) The CPU utilization aggregated across all consumer groups.
Read I/O Rate (requests per second) The rate of I/O read requests per second.
Read I/O Throughput (MB/s) The I/O throughput of the database for read requests.
Total I/O Rate (requests per second) The total rate of I/O read and write requests per second.
Total I/O Throughput (MB/s) The total I/O throughput of the database for both read and write requests.
Write I/O Rate (requests per second) The rate of I/O write requests per second.
Write I/O Throughput (MB/s) The I/O throughput of the database for write requests.

Database Wait Time

This section provides information on the metrics in the Database Wait Time category, which monitor wait time by category.

Target Version Evaluation and Collection Frequency
23ai and later Every 15 minutes
Metric Name Description
Wait Time: Others The wait time across wait events that do not fall into specific, well-defined categories.
Wait Time: Total The total amount of wait time across all wait events and categories.
Wait Time: User I/O The amount of wait time for user-initiated input/output operations.

Memory Usage

This section provides information on the metric in the Memory Usage category.

Target Version Evaluation and Collection Frequency
23ai and later Every 15 minutes
Metric Name Description
Total Memory (MB) The total amount of memory used by the database.

Response

This section provides information on the metrics in the Response category.

Target Version Evaluation and Collection Frequency
23ai and later Every 2 minutes
Metric Name Description
Primary Database Name The name of the primary database.
Status The status of the primary database. Possible values are:
  • 1: The primary database is up.
  • 0: The primary database is down.
Status of True Cache Instance The status of the True Cache. Possible values are:
  • HEALTHY
  • An Oracle error, for example: ORA-01034: The Oracle instance is not available for use. Start the instance.
True Cache Name The name of the True Cache.

True Cache Error Messages

This section provides information on the metrics in the True Cache Error Messages category.

Target Version Evaluation and Collection Frequency
23ai and later Every 10 minutes
Metric Name Description
Destination ID A numeric value that identifies which True Cache the event is associated with.
Error Code The error ID pertaining to the event.
Facility The facility that encountered the event. Possible values are:
  • Crash Recovery
  • Log Transport Services
  • Log Apply Services
  • Role Management Services
  • Remote File Server
  • Fetch Archive Log
  • Data Guard
  • Network Services
Message The text message describing the event.
Severity The severity of the event. Possible values are:
  • Informational
  • Warning
  • Error
  • Fatal
  • Control
Timestamp The date and time the error message was recorded.

True Cache Hit Ratios and Lags

This section provides information on the metrics in the True Cache Hit Ratios and Lags category.

Target Version Evaluation and Collection Frequency
23ai and later Every 15 minutes
Metric Name Description
Apply Lag (seconds) The number of seconds the data in True Cache is behind the primary database.
Flash Hit Ratio (%) The percentage of data requests served from the attached flash disk.
RAM Buffer Hit Ratio (%) The percentage of data requests served from the fast RAM memory.
Transport Lag (seconds) The number of seconds by which the transport of redo to True Cache lags behind the generation of redo on the primary database.
True Cache Hit Ratio (%) The percentage of query requests against True Cache that are satisfied directly, rather than having to fetch data from the primary database.

True Cache Process Counts

This section provides information on the metric in the True Cache Process Counts category.

Target Version Evaluation and Collection Frequency
23ai and later Every 10 minutes
Metric Name Description
Process Count The number of processes with this role.
Role The role of the process. Possible values are:
  • True Cache data request send
  • True Cache data block receive

True Cache Statistics

This section provides information on the metrics in the True Cache Statistics category.

Target Version Evaluation and Collection Frequency
23ai and later Every 15 minutes
Metric Name Description
Unit The unit of the True Cache statistic.
Value The value of the True Cache statistic.