14 Monitoring Cache Trends with Statistics

See Also:

Oracle Application Server Performance Guide for performance tuning tips

This chapter describes how to gather performance statistics to monitor cache operation trends.

This chapter contains these topics:

Monitoring OracleAS Web Cache Health
Configuring End-User Performance Monitoring
Gathering End-User Performance Data
Viewing Cache Performance Statistics
Viewing Origin Server Performance Statistics

Note that while this chapter focuses on the use of OracleAS Web Cache Manager, you can use Oracle Enterprise Manager 10g Application Server Control Console and Oracle Enterprise Manager 10g Grid Control Console to monitor many of the same performance statistics described in this chapter. See Chapter 6 and the Oracle Application Server Administrator's Guide for further information about using Oracle Enterprise Manager 10g to monitor Oracle Application Server components.

If after monitoring metrics from either OracleAS Web Cache Manager or Enterprise Manager you need additional performance metrics, point your browser to the following URL:

http://web_cache_hostname:web_cache_stats_port

The default port is 9402. This URL takes you to the Oracle Web Cache Internal Diagnosability Monitor page, which provides additional information about hits and misses.

See Also:

"Task 8: Configure OracleAS Web Cache with Operations Ports" for further information about configuring the statistics monitoring port

Note:

After making a Statistics port property change in the Operations Ports page (Ports > Operations Ports) in OracleAS Web Cache Manager, ensure that the cache server process is restarted. If it is not, then the Monitoring pages (Web Cache Statistics, Health Monitor, Origin Server Statistics, and Popular Requests) report the following error:

Failure obtaining statistics from Web Cache cache server: error in connect. Please check that the cache server is up and running.

See "Task 12: Restart OracleAS Web Cache" for instructions on applying configuration changes and restarting the cache server process with command-line tools or OracleAS Web Cache Manager.

Monitoring OracleAS Web Cache Health

OracleAS Web Cache provides a health monitor that enables you to quickly access information about overall cache performance.

To monitor overall cache health from OracleAS Web Cache Manager:

In the navigator frame, select Monitoring > Health Monitor.

The Health Monitor page appears in the right pane.
From the For Cache list, select the cache and click View. If you have not configured a cache cluster, this field displays the cache to which you are connected.
From the Auto Refresh list, select the frequency at which you want the statistics refreshed and click Set.

If you select Never, then the page will not be refreshed again. If you want the statistics refreshed now, click Refresh Now.

Table 14-1 through Table 14-3 describe the statistics for this page.

Table 14-1 describes the general statistics.

Table 14-1 OracleAS Web Cache Health Monitor: General Statistics

Statistic	Description
Current Time	The time when this page was generated
Current Web Cache Start Time	The time when OracleAS Web Cache was started
Time Since Start	The length of time that OracleAS Web Cache has been operating since it was started. Time is denoted in `days/hours/minutes/seconds`.
Total Number of Requests Served by Current Web Cache	Accumulated number of requests that OracleAS Web Cache has served since it was started See Also: "Viewing Cache Performance Statistics" to view detailed statistics for OracleAS Web Cache

Table 14-2 describes the statistics shown in the Requests Served by Origin Servers table, which lists the number of requests served to the selected cache by the origin servers.

Table 14-2 Requests Served by Origin Servers

Statistic	Description
Requests Served by Origin Servers	Name of the origin server and the port number from which the origin server is listening for OracleAS Web Cache requests.
Proxy Server	YES specifies that the server is a proxy server. NO specifies that the server is an application Web server.
Up/Down	The status of the origin server at the time that OracleAS Web Cache last attempted to communicate with that origin server. (OracleAS Web Cache attempts to reach the origin server only for specific purposes, such as retrieving responses for a cache miss.) UP specifies that the last communication with the server was successful. DOWN specifies that the server is down. If this is the last server in a single or multiple server configuration, OracleAS Web Cache continues to forward requests. If this is not the last server, no new requests will be sent to server. However, OracleAS Web Cache will poll the server until it is back online.
Since	Date and time when the origin server was last known to be up or down.
Total Requests Served	Number of client requests, such as Web browser requests, resolved by this origin server.
Average Latency	Average amount of time for the client requests to be resolved.

Table 14-3 describes the statistics in the Serving Requests/Second Now table.

Table 14-3 Serving Requests/Second Now Statistics

Statistic	Description
Stale Serves from Current Web Cache	Objects in the cache that have expired or that have been invalidated, but have not yet been refreshed from the origin servers
Fresh Serves from Current Web Cache	Objects in the cache that are still valid The health bar provides a graphical view of the number of client requests resolved for each second.

Statistic

Description

Stale Serves from Current Web Cache

Objects in the cache that have expired or that have been invalidated, but have not yet been refreshed from the origin servers

Fresh Serves from Current Web Cache

Objects in the cache that are still valid

The health bar provides a graphical view of the number of client requests resolved for each second.

Configuring End-User Performance Monitoring

Using Oracle Enterprise Manager 10g Grid Control Console or OracleAS Web Cache Manager, you can monitor the response time of your applications by viewing information about how quickly the responses are delivered to the end users. From the time a user enters the Web site until they exit, you can monitor which URLs they view and view reports about the response times the end user has experienced.

You can view this information using Grid Control Console. End-user performance monitoring is part of the Application Service Level Management feature.

To configure OracleAS Web Cache for end-user performance monitoring, ensure that the following prerequisites are fulfilled:

Configure a network load balancer for a deployment supporting multiple OracleAS Web Cache servers. The network load balancer enables OracleAS Web Cache to receive requests from the same clients.
Ensure that software for Grid Control Console is configured on the network.

You can enable end-user performance monitoring for a specific cache or for a site. The basic steps are:

Follow instructions in the Oracle Enterprise Manager Advanced Configuration to create a Web Application target in Grid Control Console.

A Web Application is an Enterprise Manager target that consolidates all the components of your Web application and displays the availability and performance of the application
Using Oracle Enterprise Manager 10g Application Server Control Console or OracleAS Web Cache Manager, enable End-User Performance Monitoring for a cache or a site. See "Enabling End-User Performance Monitoring" for instructions.
From Grid Control Console, navigate to the Web Application home page, and click the Administration tab to display the Web Application Administration page. From Grid Control Console, on the Configure Web Application Web Caches page, start the collection of data and specify an interval for the collection.
Click Configure Web Application Web Caches to start the collection of data and specify an interval for the collection.
See Also:

"Overview of Configuring End-User Response Time Monitoring" in Enterprise Manager Online Help for instructions

Oracle Enterprise Manager Advanced Configuration

Enabling End-User Performance Monitoring

To enable end-user performance monitoring for a cache or a site in Application Server Control Console, navigate to Web Cache Home page > Administration tab > Properties > Web Cache > End-User Performance Monitoring.

See Also:

"Configuring End-User Performance Monitoring" in Enterprise Manager Online Help for instructions

To enable end-user performance monitoring for a cache or a site in OracleAS Web Cache Manager:

In the navigator frame of OracleAS Web Cache Manager, select Logging and Diagnostics > End-User Performance Monitoring.
You can enable monitoring for a particular cache or for an entire site.
- To enable monitoring for a particular cache, in the End-User Performance Monitoring page, select the cache from the Cache-Specific End-User Performance Monitoring section. Then, click Enable.
- To enable monitoring for the entire site, in the End-User Performance Monitoring page, select the site from the Site-Specific End-User Performance Monitoring section. Then, click Enable.
Note the following:
- If you enable monitoring for a specific cache, but you disable monitoring for a site, monitoring is performed for all the sites in that cache node except for the site for which it is disabled.
  
  If a request does not match any of the sites for which monitoring is enabled, the request will not be monitored.
- If you disable monitoring for a cache, monitoring is not performed for any of the sites of that cache node.
- For a site, you can specify end-user performance monitoring rules.
When end-user performance monitoring is enabled for a cache, Grid Control Console and OracleAS Web Cache Manager monitor all requests that are routed through the cache. When end-user performance monitoring is enabled for a site, Grid Control Console and OracleAS Web Cache Manager monitor all of the Web pages on your Web site and provide you with information about how the pages are responding to customer requests. Using Grid Control Console, you can sort this information by URL, region, domain, visitor, and Web server.
Optionally, select URLs to monitor or not monitor by creating site-specific monitoring rules as described in "Selecting URLs to Monitor".
Configure OracleAS Web Cache to use the End-User Performance Monitoring access log format, as described in "Configuring Access Logs".
Start end-user performance monitoring:
1. From Grid Control Console, on the Configure Web Application Web Caches page, click Collecting.
2. In the Interval (minutes) column, enter the interval at which to collect performance data.
3. Click OK.

Selecting URLs to Monitor

For each site, you can further refine which Web pages are monitored, by specifying regular expressions or path substrings.

In the Set Up End-User Performance Monitoring page of Application Server Control Console (Web Cache Home page > Administration tab > Properties > Web Cache > End-User Performance Monitoring), click Filtered or All to configure the end-user performance monitoring rules for the selected site.

See Also:

"Configuring End-User Performance Monitoring" in Enterprise Manager Online Help for instructions

In OracleAS Web Cache Manager, take the following steps:

In the navigator frame, select Logging and Diagnostics > End-User Performance Monitoring.
In the Site-Specific End-User Performance Monitoring section of the End-User Performance Monitoring page, select the site, then click View.
To add a site-specific rule, click Create Site-Specific Rule.

The Create End-User Performance Monitoring Rule page is displayed.
In the URL Expression field, specify the URL expression. Note the following information, which is dependent on the Expression Type selected:
- Path Substring: Enter a path substring.
  
  The substring is interpreted literally, including reserved regular expression characters. These characters include periods (.), question marks (?), asterisks (*), brackets ([]), curly braces ({}), carets (^), dollar signs ($), and backslashes (\).
  
  For example, if you enter a substring of down, any of the following URLs match the expression:
```
http://www.company.com/wireless/downloads/index.htm
http://www.company.com/support/updown.htm
http://www.company.com/support/shutdown_gdlines.htm
```
- Regular Expression: Enter the regular expression. Remember to use "^" to denote the start of the URL and "$" to denote the end of the URL.
  
  Regular expression syntax is based on the POSIX 1003 extended regular expressions for URLs, as supported by Netscape Proxy Server 2.5.
  
  When using POSIX regular expression, keep the following syntax rules in mind:
  - If these characters are not used, POSIX assumes a substring match. For example, ^/a/b/.*\.gif$ will match GIF files under /a/b or any of its subdirectories. /a/b/.*\.gif, on the other hand, could match /x/y/a/b/c/d.gift.
  - Use a period (.) to match any one character
  - Use a question mark (?) to match zero or one occurrence of the character that it follows.
  - Use an asterisk (*) to match zero or more occurrences of the pattern that it follows.
  - Use a backslash (\) to escape any special characters, such as periods (\.), question marks (\?), or asterisks (\*).
  For example, to monitor all URLs beginning with /machine/doc and ending in .gif, enter the following expression:
```
^/machine/doc/.*\.gif$
```
From the list in the Expression Type column, select one of the following options:
- Path Substring: Applies the monitoring rule to objects matching a substring of a path
- Regular Expression: Applies the monitoring rule to objects matching regular expression syntax
For Monitoring Policy, select Monitor or Don't Monitor for the rule.
Click Submit.
To create another monitoring rule, click Edit, Insert Above, or Insert Below. Then, repeat Steps 4 through 7.
If you have more than one monitoring rule, you can use the Move Up and Move Down buttons on the End-User Performance Monitoring page to prioritize the rules. Higher priority rules are processed first. The highest priority rule appears first in the list. The lower the number listed in the priority column, the higher the priority. For example, the highest priority rule is assigned a priority of one (1).

For a regular expression that matches objects or a subset of objects that you do not want to monitor, give the rule that specifies Don't Monitor a higher priority than the rule that specifies Monitor. For example, if you want all URLs containing /cec/cstage?ecaction=ecpassthru to be monitored except for /cec/cstage?ecaction=ecpassthru2, you would enter the rules in the following order:
1. ^/cec/cstage\?ecaction=ecpassthru2, Don't Monitor
2. ^/cec/cstage\?ecaction=ecpassthru.*, Monitor
If the order were reversed, all objects starting with /cec/cstage?ecaction=ecpassthru would be monitored, including /cec/cstage?ecaction=ecpassthru2.

Gathering End-User Performance Data

You can view this information using Grid Control Console. End-user performance monitoring is part of the Application Service Level Management feature.

See Also:

"Configuring End-User Performance Monitoring" for information about configuring end-user performance monitoring.

Alternatively, you can use OracleAS Web Cache Manager to access the data, but this feature is for evaluation purposes only and is currently unsupported. For more complete analysis and reporting, use the fully-supported Grid Control Console Application Service Level Management.

With OracleAS Web Cache Manager, you can view the output in HTML or write it to a comma-delimited file, which can be imported into spreadsheet tools for viewing and analysis. The output provides information about the URLs or domains accessed and the average, minimum, and maximum latency of the requests to each URL.

Note that generating the output may take several minutes or hours to complete, depending on the log file size. Because this operation is processed on the OracleAS Web Cache server, perform this operation during non-peak hours to maintain the performance of your cache.

To use this feature, take the following steps:

Configure the cache for end-user performance monitoring, as described in "Configuring End-User Performance Monitoring".
In the navigator frame of OracleAS Web Cache Manager, select Monitoring > End-User Performance Analysis.

The End-User Performance Analysis page appears.
In the Specify Access Log File for Analysis field, specify the full file specification for the access log that you want to analyze.
Click Submit.

OracleAS Web Cache Manager displays the Analyzing End-User Performance dialog box, which provides progress messages. Do not close this dialog box.
When the operation is complete, the Analyzing End-User Performance dialog box displays methods of viewing the results. Select one of the following:
- To view the output in HTML, select View output in HTML. The output is displayed in a browser window. To specify how the information is sorted, select one of the following from the links in the browser window:
  - By URL: Access log entries are sorted by URL.
  - By Domain: Access log entries are sorted by domain.
  - By URL (Hourly): Access log entries are sorted by hour, then by URL.
  - By Domain (Hourly): Access log entries are sorted by hour, then by domain.
- To download the output to a comma-delimited (.csv) file, select one of the following:
  - By URL: Access log entries are sorted by URL.
  - By Domain: Access log entries are sorted by domain.
  - By URL (Hourly): Access log entries are sorted by hour, then by URL.
  - By Domain (Hourly): Access log entries are sorted by hour, then by domain.
  You are prompted to save or open the file. You can view the file in any application, such as Microsoft Excel, that supports comma-delimited files.

Viewing Cache Performance Statistics

To monitor performance for a cache in OracleAS Web Cache Manager:

In the navigator frame, select Monitoring > Web Cache Statistics.

The Web Cache Statistics page appears.
From the For Cache list, select the cache and click View.
From the For Site list, select the Web site for which to view statistics. Click View.
From the Auto Refresh list, select the frequency at which you want the statistics refreshed, and click Set.

If you select Never, then the page will not be refreshed again. If you want the statistics refreshed now, click Refresh Now.

Table 14-4 through Table 14-8 describe the statistics on this page.

Table 14-4 describes the general statistics about the cache.

Table 14-4 OracleAS Web Cache Statistics: General Statistics

Statistic	Description
Current Cache Start Time	The time when OracleAS Web Cache was started or restarted
Time Since Start	The length of time that OracleAS Web Cache has been operating since it was started or restarted. Time is denoted in `days/hours/minutes/seconds`.
Current Cache Reset Time	The time when the statistics were last reset
Time Since Reset	The length of time since the statistics were last reset

Table 14-5 describes the statistics provided by the Cache Overview table, which provides an overview of cache performance.

Table 14-5 OracleAS Web Cache Statistics: Cache Overview

Statistic	Description
Number of Objects in Cache	Number of objects stored in OracleAS Web Cache, plus the number of objects in transit through the cache. The number includes objects that have expired or have been invalidated but that have not been deleted from the cache.
Size of Objects in Cache	Size of the contents of the objects currently in the cache. This size does not reflect the total size needed to cache the objects because it does not include object header information or object overhead.
Total Bytes Served	Total number of bytes served to clients, such as browsers
Total Bytes Saved by Compression	Additional bytes that would be sent to clients if in-cache compression is disabled
Current Number of Open Connections	Current number of incoming open connections to the OracleAS Web Cache server and outgoing open connections to the origin servers. You can adjust the limit of connections in the Resource Limits page (Properties > Resource Limits).
Configured Maximum Cache Size	The maximum cache size. You can adjust the maximum size of the cache in the Resource Limits page (Properties > Resource Limits).
Current Allocated Memory	The physical size of the cache. The physical size of the cache is the amount of data memory allocated by OracleAS Web Cache for cache storage and operation. This number is always smaller than the process size shown by operating system statistics because the OracleAS Web Cache process, like any user process, consumes memory in other ways, such as instruction storage, stack data, thread, and library data.
Current Action Limit	Ninety-five percent of the Configured Maximum Cache Size. This number is usually larger than the Current Allocated Memory. See "Cache Memory" for more information about the relationship among Current Action Limit, Configured Maximum Cache Size, and Current Allocated Memory.

If you have a cache cluster, the Detailed Statistics link appears. This link displays the Web Cache Detailed Statistics page, which is described in "Viewing Detailed Statistics for a Cache Cluster".

Table 14-6 describes the Requests Served table. This table provides information about the number or percentage of requests OracleAS Web Cache: has served on average for each second for the last ten seconds (Recent column), has served since it was started (Since Start column), and has served since the metrics were reset (Since Reset column).

Table 14-6 OracleAS Web Cache Statistics: Requests Served

Statistic	Description
Total Requests Served	Accumulated number of browser, peer cache, and ESI requests that OracleAS Web Cache has served since it was started or restarted
Average Requests Served	Average number of client, peer cache, and ESI requests served for each second
Fresh Hits	Percentage of client requests resolved by objects in the cache This percentage should be high, except when objects are being invalidated.
Stale Hits	Percentage of client requests resolved by objects that have expired or have been invalidated, but for which updated version have not yet been retrieved from the origin servers. As objects are invalidated or expired, the percentage of stale hits will increase. The percentage will decrease as OracleAS Web Cache retrieves updated content from the origin servers. If the percentage does not decrease, it could indicate a bottleneck on the origin servers.
Cacheable Misses	Percentage of client requests that were not served directly by OracleAS Web Cache, but were served by OracleAS Web Cache after it fetched the content from the origin server. In a cache cluster, this number includes requests from peer caches.
Noncacheable Misses	Percentage of client requests for non-cacheable objects that were not served by OracleAS Web Cache.
Refreshes	Percentage of objects that OracleAS Web Cache has refreshed from the origin servers
Compressed Hits	Percentage of total requests served by the cache in compressed form
Compressed Misses	Percentage of total requests retrieved from the origin server and compressed by OracleAS Web Cache before serving

Table 14-7 describes the Cache Errors table. The Cache Errors table provides metrics about the error pages served since OracleAS Web Cache was started (Since Start column) or when the metrics were reset (Since Reset column).

Table 14-7 OracleAS Web Cache Statistics: Errors Served

Statistic	Description
Network Error	Number of error pages that OracleAS Web Cache has served to clients due to a network error
Site Busy Error	Number of error pages that OracleAS Web Cache has served to clients due to a busy Web site error
ESI Uncaught Exception	Number of errors that OracleAS Web Cache has returned to a client when an uncaught exception occurred in the cache during ESI parsing or processing
ESI Default Fragment	Number of error pages that OracleAS Web Cache has served when an uncaught exception occurs in the application during ESI parsing or processing

Table 14-8 describes the Invalidations table, which provides metrics on the invalidation requests served since OracleAS Web Cache was started (Since Start column) or when the metrics were reset (Since Reset column).

Table 14-8 OracleAS Web Cache Statistics: Invalidations

Statistic	Description
Total Invalidation Requests	The number of invalidation requests processed
Total Invalidation Objects	The total number of objects invalidated

Viewing Detailed Statistics for a Cache Cluster

If you have a cache cluster, you can view detailed statistics for the caches in that cluster.

To view these detailed statistics in OracleAS Web Cache Manager:

In the navigator frame, select Monitoring > Web Cache Statistics.

The Web Cache Statistics page appears.
Click the Detailed Statistics link located at the top of the Cache Overview table.

The Detailed Web Cache Statistics page appears.
From the For Cache list, select the cache and click View.

If you select a specific cache, then information presented in the Web Cache Statistics page displays, which is described in "Viewing Cache Performance Statistics". In addition, the Cache Overview table in this page shows metrics for owned content and on-demand content.

If you select All Caches, then Cluster Web Cache Statistics view of this page displays. Table 14-9 describes the statistics for this view.
From the For Site list, select the Web site for which to view statistics. Click View.
From the Auto Refresh list, select the frequency at which you want the statistics refreshed, and click Set.

If you select Never, then the page will not be refreshed again. If you want the statistics refreshed now, click Refresh Now.

Table 14-9 Cluster Web Cache Statistics

Statistic	Description
Number of Objects in All Caches	Total number of objects stored in all caches in the cache cluster, plus the number of objects in transit through a cache. The number includes objects that have expired or have been invalidated, but that have not been deleted from a cache.
Size of Objects in All Caches	Size of the contents of the objects currently in all caches in the cache cluster. This size does not reflect the total size needed to cache the objects because it does not include object header information or object overhead.
Total Requests Served by All Caches	Total accumulated number of client, peer cache, and ESI requests that all caches in the cache cluster have served since each cache was started or restarted.
Current Hit Rate in All Caches	Percentage of total requests resolved by objects in all caches in the cache cluster
Current Miss Rate in All Caches	Percentage of total requests to all caches in the cache cluster that were retrieved from the origin server

Viewing Origin Server Performance Statistics

To monitor origin server performance in OracleAS Web Cache Manager:

In the navigator frame, select Monitoring > Origin Server Statistics.

The Origin Server Statistics page appears.
From the For Cache list, select the cache and click View.

If you have not configured a cache cluster, this field displays the current cache (the cache to which you are connected.)
From the Auto Refresh list, select the frequency at which you want the statistics refreshed and click Set.

If you select Never, then the page will not be refreshed again. If you want the statistics refreshed now, click Refresh Now.

Table 14-10 through Table 14-12 describe the statistics for this page.

Table 14-10 describes the general information about the origin servers, that is, application Web servers or proxy servers, displayed on this page.

Table 14-10 Origin Server Statistics

Statistic	Description
Origin Server: hostname	Name of the origin server and the port number from which the server is listening for OracleAS Web Cache requests.
Origin Server: proxy server	YES specifies that the server is a proxy server. NO specifies that the server is an application Web server.
Up/Down Time	up/down: The status of the origin server at the time that OracleAS Web Cache last attempted to communicate with that origin server. (OracleAS Web Cache attempts to reach the origin server only for specific purposes, such as retrieving responses for a cache miss.) UP specifies that the last communication with the server was successful. DOWN specifies that the server is down. If this is the last server in a single or multiple server configuration, OracleAS Web Cache keeps a connection open to the server for requests. If this is not the last server, then no new requests will be sent to server. However, other active servers will poll the downed server until it is back online. since: Date and time when the origin server was last known to be up or down
Completed Requests	number/sec: Current number of requests that the origin server has processed for each second. The number is the average for each second during the last ten-second interval. max/sec: Maximum number of requests that the origin server has processed for each second during the last ten-second interval.
Latency	avg this interval: Average time this origin server has taken to process and reply to requests which it has received from this OracleAS Web Cache, over the last 10 seconds. avg since start: Average time this origin server has taken to process and reply to requests which it has received from this OracleAS Web Cache, since OracleAS Web Cache has been started.
Load	now: Current number of connections from OracleAS Web Cache that the origin server has open. The number is the average for each second during the last ten-second interval. max: Maximum number of connections that the origin server has had open at one time. Note: Consider increasing the capacity of an origin server if the max connections is close to the server's capacity. You can increase capacity in the Origin Servers page (Origin Servers, Sites, and Load Balancing > Origin Servers).
Active Sessions	Active sessions are based on the Internal-Tracking session binding mechanism configured. See "Bind a Session to an Origin Server". now: Current number of active sessions from OracleAS Web Cache to the origin servers. max: Maximum number of active sessions that the origin server has had open at one time.

Table 14-11 describes the type of errors listed in the Errors Served table, which lists the following for each type of errors served:

Number this second: Current number error pages that OracleAS Web Cache is serving
Total: Total number of error pages that OracleAS Web Cache has served since the cache was last restarted

Table 14-11 Errors Served

Type	Description
Network Error	Error pages that OracleAS Web Cache has served to clients due to a network error
Site Busy Error	Error pages that OracleAS Web Cache has served to clients due to a busy Web site error
ESI Uncaught Exception	Number of errors that OracleAS Web Cache has returned to a client when an uncaught exception occurred during ESI parsing or processing
ESI Default Fragment	Number of error pages that OracleAS Web Cache has served to a client when an uncaught exception occurs in the application during ESI parsing or processing

Table 14-12 describes the statistics in the Origin Server Backlog table.

Table 14-12 Origin Server Backlog Statistics

Type	Description
Now	Current number of requests for the cache that are awaiting processing by the application Web server.
Max	Maximum number of requests for the cache that are awaiting processing by the application Web server.