MAXSUBSCRSTAGESIZE

Specifies the maximum size of the staging space that is used to stage replicated changes for commit groups (Db2® Units of Recovery) for a single subscription and the maximum number of completed non-empty commit groups to keep in the staging space at one time. The staging space is allocated from above the bar (64-bit addressable) storage that is controlled by the Storage Manager component.

The first value provides a means of limiting the use of z/OS's real storage resources by InfoSphere® CDC when it is mirroring tables. The staging space is normally backed by above the bar storage (64-bit addressable storage) which is paged to z/OS® Auxiliary Storage. Extremely large commit groups can cause InfoSphere CDC to store large volumes of data in the staging space, consuming corresponding amounts of above the bar storage and auxiliary storage. While it is expected that good application design will limit the size of commit groups, the MAXSUBSCRSTAGESIZE keyword provides a means of stopping InfoSphere CDC from using excessive resources if this is not the case.

A staging space is associated with each subscription created in Management Console. If the content of a staging space nears capacity, InfoSphere CDC generates a warning message (CHC1532W). If this message is seen, you should consider increasing the maximum size to reduce the risk of reaching the limit. If the content of a staging space reaches the maximum size, InfoSphere CDC generates an error message (CHC1524E), and automatically ends replication for the subscription.

When specifying the first value, you identify the maximum number of kilobytes (K or k), megabytes (M or m), gigabytes (G or g), or bytes (the default unit if a recognized letter is not specified) that can be stored in a staging space.

The second value indicates the maximum number of completed non-empty commit groups to keep in the staging space at one time. This allows InfoSphere CDC to continue to stage commit groups while simultaneously transmitting a completed commit group.

The staging space is allocated through the Storage Manager. Care should be taken to specify a large enough value on the STG64LIMIT keyword to accommodate the staging spaces used by all source subscriptions.

This keyword is optional.

Default Setting—(2G, 10)

Minimum Setting (for second value)—(5M, 1)

Maximum Setting—(127G, 255)