Replication Type and Parameters

Most of the options available with the fts setrepinfo command determine the replication parameters to be associated with the fileset; the primary exceptions are the -change and -clear options, which are described later in this section. Replication parameters define the time intervals used by Cache Managers on client machines that are accessing data from the read-only replicas and Replication Servers on File Server machines that house the replicas. Descriptions of the replication parameters follow; each parameter is set with an option of the same name. (Note that the term replication parameter is used to refer to the replication intervals that are defined for a fileset with the fts setrepinfo command, not to the parameters of the command.)

The following parameters apply to both Release Replication and Scheduled Replication:

· MaxAge specifies the amount of time the Cache Manager distributes data cached from a read-only replica without attempting to verify that the data is current. The Replication Server maintains information about the currentness of a read-only replica, which it communicates to the Cache Manager via the File Exporter. For Scheduled Replication, a replica must remain current with respect to the read/write source fileset; for Release Replication, a replica must remain current with respect to the read-only replica that resides on the same File Server machine as the read/write source fileset.

· FailAge specifies the amount of time the Cache Manager distributes data cached from a read-only replica if the data cannot be verified as current. The difference between FailAge and MaxAge is the amount of time the Cache Manager continues to distribute data cached from a read-only replica after the data cannot be verified as current. An effective FailAge value is greater than or equal to the MaxAge value.

· ReclaimWait specifies the amount of time the File Exporter waits before it reclaims storage space from deleted files (those not referred to by any directory). It also determines the frequency of the Cache Manager's keep-alive messages to the Replication Server.

The Cache Manager sends keep-alive messages to indicate that it is still using files from a read-only replica. A file that is being accessed from a replica remains available as long as the Cache Manager continues to notify the Replication Server that the file is still in use and the Replication Server continues to forward these notifications to the File Exporter. This is true even if the file has been removed from all directories on the read/write fileset in the interim. To prevent the File Exporter from reclaiming storage space that was occupied by deleted files, the Cache Manager sends keep-alive messages more frequently than the ReclaimWait interval.

The following parameters apply only to Scheduled Replication:

· MinRepDelay specifies how long the Replication Server waits after a read/write fileset changes before it attempts to get a new copy of the fileset. The Replication Server tracks the currentness of replicas by maintaining a whole-fileset token for each fileset. If a Cache Manager changes the read/write fileset, the Replication Server relinquishes its whole-fileset token and waits for at least the time specified by MinRepDelay before requesting a new whole-fileset token.

· MaxSiteAge controls the maximum amount of time that a replica can be out of date. The Replication Server attempts to keep a replica current within this amount of time. A MaxSiteAge value is stored with each site; the MaxSiteAge for a site is set with the fts addsite command.

· DefaultSiteAge is the default value to be used as the MaxSiteAge for a replication site if that value is not set with the fts addsite command.

The following table summarizes the six parameters just described. For each parameter, the table describes the command with which the parameter is set, its default value, its usage (if any) with Release Replication, and its usage with Scheduled Replication; usage descriptions include details on the dependencies between the different parameters. Refer to this table when using the fts setrepinfo (or fts addsite) command to specify the replication parameters for a fileset (or site).

Note: Unless it is absolutely necessary to change them, it is recommended that you use the default parameters (with the exception of MaxAge) that are listed in the table.

Descriptions of Replication Parameters

Parameter	Default	Release Replication	Scheduled Replication
MaxAge (fts setrepinfo)	2 hours	Required only if FailAge is specified	Required only if FailAge, MinRepDelay, or DefaultSiteAge is specified
FailAge (fts setrepinfo)	1 day or twice MaxAge, whichever is larger	Optional	Required only if MinRepDelay or DefaultSiteAge is specified
ReclaimWait (fts setrepinfo)	18 hours	Required only if FailAge is specified	Required only if FailAge, MinRepDelay, or DefaultSiteAge is specified
MinRepDelay (fts setrepinfo)	5 minutes or one-quarter of DefaultSiteAge, whichever is smaller	Not applicable	Required only if FailAge or DefaultSiteAge is specified
MaxSiteAge (fts addsite)	DefaultSiteAge	Not applicable	Required only if DefaultSiteAge is not specified
DefaultSiteAge (fts setrepinfo)	One-quarter of MaxAge	Not applicable	Optional

The system uses the guidelines listed in the table above to calculate default values for each of the parameters unless you specify

· FailAge for Release Replication

· FailAge, MinRepDelay, or DefaultSiteAge for Scheduled Replication

Once you specify one of these parameters, the system no longer performs any default calculations; you must specify values for all applicable parameters. The exception is DefaultSiteAge for Scheduled Replication, which is always optional. However, if the other parameters specified with the fts setrepinfo command are supplied, the system does not calculate a default value for DefaultSiteAge; you must specify the MaxSiteAge for each replication site with the fts addsite command. Also, because the MinRepDelay, MaxSiteAge, and DefaultSiteAge parameters do not apply to Release Replication, they are recorded but otherwise ignored if they are specified for a fileset that uses Release Replication. (They are used if the fileset's style of replication is ever changed to Scheduled Replication.)

Setting Replication Type and Parameters

To set a fileset's replication type and parameters, do the following:

1. Verify that you have the necessary privileges. You must be included in the admin.fl file on each Fileset Database machine or own the server entry for each machine on which a version of the fileset resides. If necessary, issue the bos lsadmin command to verify the members of an administrative list.

Note: If you use the command's -change option to change a fileset's existing replication type from Release to Scheduled, you must also be included in the admin.ft file on the machine on which the read/write fileset resides if a replica actually resides at the replication site on that machine. (The first replication site defined for a fileset that uses Release Replication must be on the same File Server machine as the read/write fileset.)

2. Enter the fts setrepinfo command to set the replication parameters for the read/write fileset that is to be replicated. To use the default parameters described in the table above, enter only the fileset name or ID number and the replication type. To specify one or more of the parameters, refer to the table for information on which parameters apply for the two types of replication and the dependencies between the parameters.

Enter interval values as integers with the following abbreviations to designate units: d for days, h for hours, m for minutes, and s for seconds. For example, to indicate 3 days and 2 hours, enter 3d2h. At least one of the four values (days, hours, minutes, or seconds) must be provided, and the unit abbreviations (d, h, m, or s) must be used with any integer. The unit abbreviations can be uppercase or lowercase, and they can be entered in any order; for example, 3m2h is a valid entry for 2 hours and 3 minutes.

$ fts setrepinfo -fileset {name | ID} {-release | -scheduled} [-change] [-maxage interval]
[-failage interval] [-reclaimwait interval] [-minrepdelay interval] [-defaultsiteage interval]
[-clear]

The -fileset name or ID option is the complete name or ID number of the read/write DCE LFS fileset to be replicated.

The -release option specifies that Release Replication is to be used with the fileset. When initially setting the replication type, use this option or use the -scheduled option.

The -scheduled option specifies that Scheduled Replication is to be used with the fileset. When initially setting the replication type, use this option or use the -release option.

The -change option is used with -release or -scheduled to indicate that the replication type is to be changed. When changing the replication type for a fileset, you must include the -change option. (See Changing Replication Type and Parameters.)

The -maxage interval option is the value for MaxAge. An effective value must be greater than or equal to 2 minutes.

The -failage interval option is the value for FailAge. An effective value must be greater than or equal to -maxage.

The -reclaimwait interval option is the value for ReclaimWait. An effective value must be greater than 2 hours; do not specify a value less than 90 minutes.

The -minrepdelay interval option is the value for MinRepDelay. This value must be less than the MaxSiteAge specified for each replication site with the -maxsiteage option of the fts addsite command.

The -defaultsiteage interval option is the value for DefaultSiteAge. This value is used as the MaxSiteAge for a replication site if the -maxsiteage option is omitted when the fts addsite command is used to define the site.

The -clear option removes all replication parameters previously defined for the fileset. (See Changing Replication Type and Parameters.)

Changing Replication Type and Parameters

You can use the fts setrepinfo command to change the type of replication or the replication parameters that are associated with a fileset at any time after they are set. Brief descriptions of the operations used to change these values follow:

· To change some replication parameters, use the options for the parameters you want to change to indicate the new parameters.

· To change all replication parameters, use the -clear option to remove all previous replication parameters, and either use the options for the parameters you want to change to indicate the new parameters or omit the options to allow the system to calculate new replication parameters.

· To change the replication type, use the -release or -scheduled option to indicate the new type of replication to be used, and use the -change option to indicate that the type is to be changed. Although not required, you may also want to use the -clear option to clear all previous replication parameters and then reset them using parameters that are better suited to the new type of replication.

Because Scheduled Replication imposes more constraints than Release Replication, Release Replication does not require a replication site to have a MaxSiteAge. Therefore, it is likely that one or more Release Replication sites will have a MaxSiteAge of 0 (zero), which is the default value recorded for a site if no MaxSiteAge or DefaultSiteAge is specified. When changing from Release Replication to Scheduled Replication, the -defaultsiteage option must be used to set a DefaultSiteAge if any replication site does not have a MaxSiteAge and no DefaultSiteAge exists for the source fileset; otherwise, the fts setrepinfo command fails. If the command fails for this reason, reissue it, specifying a DefaultSiteAge with the -defaultsiteage parameter.

(See Setting Replication Type and Parameters, above, for details about the syntax of the fts setrepinfo command. See the table above for information about which of the command's options apply to the two types of replication and the dependencies between the parameters.)

Listing Replication Type and Parameters

You can use the fts lsfldb or fts lsft command to list information on the replication type and replication parameters defined for a fileset. (See Managing Filesets for more information on the options and output associated with these commands.)

$ fts lsfldb [-fileset {name | ID}] [-server machine] [-aggregate name] [-locked]

$ fts lsft [{-path {filename | directory_name} | -fileset {name | ID}}] [-server machine]