Foglight for SQL Server (Cartridge) 5.9.7.21


Display Name	Description
Buffer Cache Free Size	The total number of free pages on all free lists. This value is calculated as follows: <free pages> * 8K / 1024. When SQL Server needs a free memory page (for example, when reading a database page from disk into the buffer cache), and if no free pages are immediately available, the connection needing the free page will have to wait while SQL Server makes buffers available. This will result in slower performance. In the worst case, the connection will have to wait while SQL Server writes a modified page out to disk in order to make a free buffer.
Buffer Cache Hit Rate	The total number of cache hits.
Buffer Cache Hit Ratio	The ratio of physical reads to logical reads. It indicates the percentage of database page I/O requests that were satisfied from the Buffer Cache and therefore did not have to perform disk reads. This ratio measures how efficiently SQL Server is using the memory allocated to its buffer cache.
Buffer Cache Reads	The total number of cache lookups over the last few thousand page accesses.
Buffer Cache Size	The amount of memory currently allocated to the buffer cache, including database, free, and stolen pages. This size is calculated as follows: <free pages> * 8K / 1024. The Buffer Cache is an in-memory copy of recently used database pages.
Checkpoint Pages	The number of pages flushed by checkpoint or other operations that require all dirty pages to be flushed.
Database Pages	The number of pages that constitute the SQL data cache. A large change in this value indicates the database is swapping cache values from the cache. This database pages value is calculated as follows: <pages> * 8KB / 1024. SQL Server keeps a copy of its most recently used database pages in the buffer cache. When a connection needs to reference a database page, SQL Server performs a Logical I/O operation by checking the buffer cache to see if the requested page is already in memory. If the page is found in the buffer cache, a logical I/O read will be carried out; otherwise, the page is read from disk, using a Physical I/O operation.
Free Pages	The total number of free pages on all free lists. This value is calculated as follows: <free pages> * 8K / 1024. The Lazy Writer Process periodically scans all SQL Server caches, and maintains a list of such “free” pages. When SQL Server needs a free memory page (for example, when reading a database page from disk into the buffer cache), and no free pages are immediately available, the connection needing the free page must wait while SQL Server makes buffers available. This results in slower performance. In the worst case, the connection will have to wait while SQL Server writes a modified page out to disk in order to make a free buffer.
Lazy Writes	The number of buffer pages that have been modified in the buffer cache, which the Lazy Writer process is flushing to disk. A high value of lazy writes may indicate that SQL Server is running out of available space in the buffer pool cache.
Logical Page Reads	The number of logical database page reads issued. Under optimal work conditions, the SQL Server connections use logical page reads, that is: reference pages from the buffer cache. However, if the required page is not yet in the cache, it is read from disk using physical I/O operations. A high value of the logical page reads indicates that SQL Server efficiently uses the memory allocated to its buffer cache. A high value of physical page reads, on the other hand, indicates that SQL Server is finding fewer pages already in memory, and therefore has to perform more disk reads.
Page Life Expectancy	The value of page life expectancy, that is: the length of time in seconds that a database page will stay in the buffer cache without being accessed, before it is flushed out. Microsoft recommends keeping this value greater than five minutes (300 seconds). Values smaller than 300 indicate that pages are being flushed out of the cache within a small period of time. The resulting lack of pages in the buffer cache requires SQL Server to carry out more disk reads, thereby degrading its performance.
Physical Page Reads	The number of physical database page reads issued. Physical page reads are used when a connection requests a page that is not already in the buffer cache.
Physical Page Writes	The number of physical database page writes issued. Normally, SQL users do not have to wait for database write operations to complete. Most modifications to database pages are made in the buffer cache.
Read Ahead Pages	The number of pages being read from disk before they are requested, using the Read Ahead process. Read ahead is the process by which SQL Server anticipates which pages a session will require, and reads them into the Buffer Cache before they are requested by the user connection. This process is used when SQL Server determines that a session is accessing table or index pages in a sequential manner. If the sequential processing does continue, these pages will be in the cache memory when required, thereby avoiding the need to wait for an I/O operation. Read Ahead can improve queries’ performance when accessing a new table or an existing table with a new filter. However, a high level of Read Ahead activity may indicate poorly coded SQL statements or inadequate indexes.
Read Ahead Pages Rate	The rate per second at which pages were read from disk before being requested, using the Read Ahead process.
Reserved Pages	The number of buffer pool reserved pages. The reserved pages value is calculated as follows: <pages> * 8KB / 1024.
SQL Server Physical I/O Operations	Total number of pages read or written to disk. Even though some of these operations may be satisfied by the file system cache, they usually require physical disk access.
Stolen Pages	Pages “stolen” from the buffer pool to be used for miscellaneous server purposes, when Windows requires memory for another application. A large number of stolen pages may be normal for a short period (for example: if the system backup begins after a large database batch run completes). However, a constantly high value of this metric may indicate overall system memory shortage.
Target Pages	The ideal number of pages in the buffer pool. The target pages value is calculated by <pages> * 8KB / 1024.

CLR Assemblies

Purpose

This collection provides information on the security state of CLR (Common Language Runtime) assemblies.

Type

SQL Server.

Collection Sampling Intervals


Frequency Mode	Collection Interval (In Seconds)
Real-time	20
Online	60
Offline	300

Collection Metrics


Display Name	Description
Database	The database name
Is Hidden	Indicates whether there is a hidden CLR assemble within the selected database.
Is External	Indicates whether there is an external CLR assemble within the selected database.
Is Unsafe	Indicates whether there is an unsafe CLR assemble within the selected database.

Cluster Summary

Purpose

This collection provides information on the state of the currently monitored cluster environment, as shown in the Cluster Administration application.

Type

SQL Server.

Collection Sampling Intervals


Frequency Mode	Collection Interval (In Seconds)
Real-time	900
Online	900
Offline	14400

Collection Metrics


Display Name	Description
ID	The unique identifier for the specified resource in the cluster.
Parent ID	The parent ID of the node’s vertical level.
Type	The type of resource (Resource group).
Name	The resource name.
Status	The status of the cluster resource.
Comment	A brief description of the specified cluster resource (if available).
Other Data	The group to which the resource belongs.
Icon Flag	A flag indicating whether there is an error.
Take Offline Cmd	A flag indicating the existence of a command that runs when the resource goes offline.
Bring Online Cmd	A flag indicating the existence of a command that runs when the resource goes online.
Move Group Cmd	A flag indicating the existence of a command that runs when the resource is moved to another group.
Stop MSCS Cmd	A flag indicating the existence of a command that runs when the resource is stopped.
Start MSCS Cmd	A flag indicating the existence of a command that runs when the resource is started.
Running On Preferred Server	A flag indicating whether the node is running on a server that appears on the preferences list.
Controls The Current SQL Server	A flag indicating whether the node is currently controlling the SQL Server.
Running On Server	Indicates the host (server) on which the selected node is running.
Non Active Node Available	Indicates which non-active SQL Server nodes are currently not running.
Can Accept Move	A flag indicating whether the resource can accept being moved to another group.

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Foglight for SQL Server (Cartridge) 5.9.7.21 - User Guide

Buffer Cache List

Buffer Manager

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