Additional Configuration Options
This section includes optional configuration features of Enterprise Server.
This section explains what caching is and how to configure Enterprise Server to use it.
How Caching Works
Caching is best suited for sites that track multiple data sources from a single DMSII database.
Caching allows you to separate the process of delivering client-requested data from filtering that data. Cached files are filtered in advance. This lets Enterprise Server quickly respond to data requests without placing an additional resource burden on the mainframe.
In Enterprise Server, you can create one or more local sources from a single DBServer source. Each local source can specify its own unique filtering conditions. When caching is enabled, Enterprise Server applies the filtering conditions of the local source and writes the update to the local cached file. When you have multiple local sources for a single remote source, caching them will improve performance.
When a Databridge Client requests updates from a cached local source, Enterprise Server reads the updates from the cache files instead of requesting them from MCP server or reading the DMSII audit files directly.
Setting Up a Base Source Cache
To enable caching, you must first configure a base source cache. The base source cache has additional options such as whether to cache before- and after-images.
To set up a base source cache
In the right pane of the Databridge Enterprise window, right-click a base source and click Properties.
In the Base Source Properties dialog box, click [Cache].
In the Base Source Cache Properties Dialog Box, do the following:
In the Cache parent directory box, type or browse to select the directory to which cached files are written. This box enables caching.
From the When tracking, read cached files menu, specify an option to determine whether cached files can be read while tracking.
From the Wait for audit to cache options, specify how long you're willing to wait for additional updates to cache.
For Remove cache files when read n times, enter the number of Databridge Clients you expect to read this cache. If Clients are tracking only filtered sources, only cached audit files from local filtered sources will be deleted; cache files for base sources will need to be removed manually.
Select the check box Both before-images and after-images for modifies if you want to store before- and after-images for modified records. Not selecting this check box results in smaller cache files but does not allow for changes to record keys.
From the Wait for audit to cache menu, select an option that determines if or how long Enterprise Server waits before checking for more updates.
Click OK, and then click [Save] in the Databridge Enterprise window.
If the [Save] button in the Databridge Enterprise window is enabled, you have made changes that have not been written to disk and therefore are not yet in effect. To put your changes into effect, click the [Save] button.
Set up a local source cache for each local source (derived from this base source) that you want to cache. If you don't have local sources you want to cache, you can populate only the base cache. When you first create a local source, all of its data set except for the restart data sets are included.
If the client requests updates from a local un-cached source, Enterprise Server will read updates from the base source's cache and apply the local source's filters. A filter is a set of conditions you can define, which allows you to replicate only the data that's relevant to a particular client. See Filtering a Local Source.
Setting Up a Local Source Cache
You can set up a local source cache from a base source. The base source provides some options that apply to all local sources derived from the base source.
To set up a cache
In the right pane of the Databridge Enterprise window, if the local source has not yet been defined, do one of the following:
Right-click a base source and select Add local (filtered) source.
Right-click a local (filtered) source, and select Properties.
Click the [Cache] button.
In the Filtered Source Cache Properties Dialog Box, select the cache settings you want, and click [OK].
Click [OK] to close the Source Properties dialog box.
Click [Save] in the Databridge Enterprise window.
Ways to Initiate Caching
To start caching, you must complete the following two steps:
Enable caching for the data source in the Base Source Cache dialog box.
Initiate the caching process. The different options for doing this are listed in the following table. The method you choose will determine your entries when you set up caching.
Manual initiation: Each time you want Enterprise Server to run caching, right-click the base source and select Start caching updates, or type the following at a command prompt:
DBEnterprise CACHE basesourcename
Scheduled initiation: Schedule a batch file that periodically runs Enterprise Server with the CACHE command via Windows scheduler.
Host initiation: The Databridge Server establishes a connection to Enterprise Server when more audit is available. (See the Databridge Server NOTIFY option in the Databridge Host Administrator's Guide.) Enterprise Server starts a batch file that runs the application with the CACHE command.
The first time you cache a particular base source, Enterprise Server begins by caching the oldest audit file available on the host. Each subsequent time Enterprise Server caches that source, it uses the AFN (from the file LastAFN.txt) to determine where to resume caching.
Enterprise Server writes a copy of all updates from DMSII audit files for the base source to the basesourcename subdirectory of the specified parent directory.
If you restart the computer or quit Enterprise Server while it is caching, you must restart caching using one of the initiation methods.
Starting Enterprise Server with the CACHE Command
You can start Enterprise Server in caching mode by using the CACHE command-line parameter.
To start caching using a command
Type the following command in a command prompt window
dbenterprise cache basesourcename [ password [ = ] "password" ] [ startafn [ [ - ] endafn | +] ]
This syntax lets you specify a starting point in addition to an ending point. You can use this option to limit the client to processing updates up to a particular AFN if the client is restricted to reading only cache files (that is, if Only is selected for When tracking, read cached files in the Filtered Source Cache Properties dialog box).
The password corresponds to the KEY (password) SOURCE option in the DBServer parameter file. The plus sign ( + ) indicates that Enterprise Server will continue caching all available audit files that follow the startafn. If you specify only a startafn, Enterprise Server will cache only the specified audit file and then stop.
Checkpoint Options Dialog Box
- In the right pane of the Databridge Enterprise window, right-click a base source or a local source and select Properties.
- In the Base Source Properties dialog box, click [Checkpoint].
Use checkpoint options to determine the frequency with which the Databridge Client commits (saves) updates from Enterprise Server for a particular data source.
The options are as follows:
|Checkpoint every quiet point
|When selected, the Databridge Client commits updates at every quiet point, (that is, when there are no transactions in progress). This makes the updates visible in the client database sooner, but incurs additional overhead updating audit locations and committing changes.
|Client may not change this
|Prevents the Client from overriding the previous setting.
|Allow checkpoints during Long Transactions
|When selected, the Databridge Client commits updates even if transactions are in progress.
|Client may not change this
|Prevents the Client from overriding the previous setting.
Checkpoint at the first quiet point after every
Enterprise Server commits a transaction group at the first quiet point after any one of the values is satisfied. A value of 0 indicates the parameter is disabled.
Enter default, minimum, and maximum values for one or more of the following:
|Number of audit blocks processed since the last commit as indicated by the Audit Block Serial Number (ABSN).
|Number of creates, deletes, or modifies since the last commit.
|Number of completed transactions since the last commit.
|Number of seconds elapsed since the last commit. This indicates the time that elapses during replication (not the time that elapsed when the updates originally took place on the host system).
If the Client specifies a value outside the permitted range, Enterprise Server will adjust the value to fall within the permitted range. If no value is specified, the default values are used.