LucidDbPerformanceCounters

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Overview

This page lists the performance counters available in LucidDB. To retrieve current settings, use the following system view query:

select * from sys_root.dba_performance_counters;

See LucidDbSystemViews#DBA_PERFORMANCE_COUNTERS for a description of the system view. These counters can also be displayed graphically in LucidDbMonitor.

The performance counters are updated every 500 ms. In some cases, the counters are cumulative for the current server instance, in which case, the name of the counter is appended with SinceInit. The same counter name without the SinceInit is a snapshot, in that it only represents activity since the last time the counter was updated.

Performance Counters List

Category Subcategory Name Description
JVM Memory
JvmMemoryUnused The amount of free memory, in bytes, in the JVM.
JvmMemoryAllocationLimit The maximum amount of memory, in bytes, that the JVM will attempt to use.
JvmMemoryAllocated The total amount of memory, in bytes, in the JVM.
Parameter Settings (See LucidDbSystemParameters for further information, in cases where the counters correspond to system parameters.)
ExpectedConcurrentStatements The value of the system parameter specifying the maximum number of concurrent statements executing at any given time. It is used by the resource governor to determine the maximum resource allocation for each statement. Corresponds to the expectedConcurrentStatements system parameter.
CacheReservePercentage The percentage of the LucidDB buffer pool that should be set aside for global resource usage. The remainder will be available to allocate to individual statements. Corresponds to the cacheReservePercentage system parameter.
CachePagesAllocated The total number of pages currently allocated in the buffer pool. Corresponds to the cachePagesInit system parameter.
CachePagesGoverned The number of buffer pool pages the resource governor has available to allocate to individual statements. The value corresponds to (100-CacheReservePercentage)/100 * CachePagesAllocated.
CachePagesAllocationLimit The upper bound for the number of pages that can be allocated in the buffer pool. Corresponds to the cachePagesMax system parameter.
Execution
DatabaseCheckpoints The number of database checkpoints executed since the last snapshot.
DatabaseCheckpointsSinceInit The number of database checkpoints executed in this server instance.
Storage
DatabasePagesAllocated The number of pages allocated in the db.dat file, corresponding to user data.
DatabasePagesOccupiedHighWaterSinceInit The maximum number of pages in use in the db.dat file during the current server instance. Unlike DatabasePagesAllocated, this count includes pages that are not user data, i.e., the two database header pages as well as other internal, metadata pages. The HighWater in the name indicates that the counter represents the maximum size the file has grown since the server was started. I.e., if a page is allocated and then later deallocated in the current server instance, that page is reflected in DatabasePagesOccupiedHighWater, but not DatabasePagesAllocated.
DatabasePagesExtendedSinceInit The number of pages that have been added to db.dat since the current server instance was started. Note that pages are added in increments according to the databaseIncrementSize system parameter.
TempPagesAllocated Same as DatabasePagesAllocated, except it reflects pages in temp.dat.
TempPagesOccupiedHighWaterSinceInit Same as DatabasePagesOccupiedHighWaterSinceInit, except it reflects pages in temp.dat.
TempPagesExtendedSinceInit Same as DatabasePagesExtendedSinceInit, except it reflects pages in temp.dat. Pages are added in increments according to the tempIncrementSize system parameter.
Buffer Pool Statistics (See LucidDbMemoryManagement for background on the buffer pool and how it is used for data caching and other activities.)
General Usage
CachePagesReserved The number of buffer pool pages currently reserved by the resource governor for currently executing statements.
CachePagesUnused The number of buffer pool pages allocated but currently not in use.
CacheDirtyPages The number of buffer pool pages that are currently dirty.
CacheRequests The number of requests made to access pages in the buffer pool since the last snapshot.
CacheRequestsSinceInit The number of requests made to access pages in the buffer pool in the current server instance.
CacheHits The number of buffer pool requests that were satisfied without a disk read since the last snapshot.
CacheHitsSinceInit The number of buffer pool requests that were satisfied without a disk read in the current server instance.
CacheVictimizations The number of times a page had to be discarded from the buffer pool to satisfy a request for another page, since the last snapshot.
CacheVictimizationsSinceInit The number of times a page had to be discarded from the buffer pool to satisfy a request for another page in the current server instance.
CachePageIoRetries The number of buffer pool requests requiring either a disk read or write that needed to be retried, since the last snapshot.
CachePageIoRetriesSinceInit The number of buffer pool requests requiring either a disk read or write that needed to be retried in the current server instance.
Read-Specific
CachePagesRead The number of disk pages read into the buffer pool since the last snapshot.
CachePagesReadSinceInit The number of disk pages read into the buffer pool in the current server instance.
CachePagesPrefetched The number of page pre-fetch requests that were successful since the last snapshot. Note that a pre-fetch request can be met either because the page is already in the buffer pool or by reading the page from disk without the need for a retry.
CachePagesPrefetchedSinceInit The number of page pre-fetch requests that were successful in the current server instance.
CachePagePrefetchesRejected The number of page pre-fetch requests that were not immediately met since the last snapshot. A pre-fetch request is not met if there is no space in the buffer pool, or if reading the page from disk requires a retry.
CachePagePrefetchesRejectedSinceInit The number of page pre-fetch requests that were not immediately met in the current server instance.
Write-Specific
CachePagesWritten The number of buffer pool pages written to disk since the last snapshot.
CachePagesWrittenSinceInit The number of buffer pool pages written to disk in the current server instance.
CacheVictimizationWrites The number of buffer pool pages written to disk while trying to locate space in the buffer pool for another page, since the last snapshot.
CacheVictimizationWritesSinceInit The number of buffer pool pages written to disk while trying to locate space in the buffer pool for another page in the current server instance.
CacheLazyWriteCalls The number of calls to the lazy page writer that resulted in at least one page being written to disk, since the last snapshot. The lazy page writer periodically checks the buffer pool for dirty pages. If the number of dirty pages falls within a threshold range, then dirty pages are flushed.
CacheLazyWriteCallsSinceInit The number of calls to the lazy page writer that resulted in at least one page being written to disk in the current server instance.
CacheLazyWrites The number of buffer pool pages written to disk by the lazy page writer, since the last snapshot.
CacheLazyWritesSinceInit The number of buffer pool pages written to disk by the lazy page writer in the current server instance.
CacheCheckpointWrites The number of buffer pool pages written to disk during checkpoints, since the last snapshot.
CacheCheckpointWritesSinceInit The number of buffer pool pages written to disk during checkpoints in the current server instance.
Miscellaneous
JvmNanoTime The current value of the system timer, in nanoseconds.