Restrictions

Before you install IBM® InfoSphere® Classic Change Data Capture for z/OS®, ensure that your data sources qualify for replication.

Restrictions for IMS data sources

Unsupported database types

Classic change data capture does not support the following IMS database types:

  • GSAM (generalized sequential access method)
  • HSAM (hierarchical sequential access method)
  • MSDB (main storage databases)
Certain logically-related databases

Logically-related databases with multiple access paths can lead to conflicting conditions that make these databases ineligible for replication. When you consider them together, the following criteria for EXIT parameters, logical relationships, and delete rules create the conflict:

  • Logical child segments with EXIT coding must have a virtual delete rule.
  • Logical parent segments with EXIT coding cannot have a virtual delete rule.

If a segment acts as both a logical parent and logical child, you cannot include an EXIT statement on that segment or any of its children. Therefore you cannot enable a table or view for change data capture that is not augmented with an EXIT statement.

Unsupported subsystem and application types

You cannot capture changes from IMS subsystems that operate in an Extended Recovery Facility (XRF) complex.

Consider these additional restrictions when you implement Classic change data capture:

  • Classic change data capture does not replicate data that you restore from image copy.
  • Classic change data capture does not replicate data that you load into the database.
  • You must register subsystems whose changes you want to capture in a shared set of RECON data sets.
  • You must catalog all IMS logs that you want to capture in a shared integrated catalog facility (ICF).
  • DASD-based logs must reside on shared DASD that any image in the source sysplex can access.
  • Changes made by applications that issue FLD calls can be captured when using IMS version 13 and when the segment is augmented with the FLD option.
  • You cannot capture changes to primary and secondary indexes.
  • The combined maximum segment lengths of all segments that are included in the table cannot exceed 32767 bytes.
  • An IMS PSB that is defined with the PSBGEN option LANG=PL/I prevents access to an IMS table for refresh. The valid options are LANG=ASSEM or LANG=COBOL.

Restrictions for VSAM sources

Supported types of data set organization
Changes can be captured from the following types of VSAM datasets:
  • Key-sequenced data sets (KSDS)
  • Entry sequenced data sets (ESDS) – the relative byte address (RBA) of an ESDS record is not captured
  • Relative record data sets (RRDS) – the relative record number (RRN) of a RRDS record is not captured.

Standard and extended format data sets are supported. The maximum RECORDSIZE that is defined for the VSAM file cannot exceed 32767 bytes.

Minimum support levels
You can capture changes from VSAM data sets using products with these minimum release levels:
  • CICS Transaction Server for z/OS (CICS TS), version 5.5 or later
  • CICS VSAM Recovery (CICS VR), version 5.1 or later
  • DFSMStvs version 2.5 or later
System Management Subsystem (SMS)
Replication logging can only be enabled for datasets under SMS control.
Exclusive lock restriction
An exclusive lock is a resource serialization mechanism that grants a single task sole read/write access to a record or data item. The locks remain held by the transaction making the change until it either issues a sync point request or terminates. CDC cannot access VSAM files that are opened exclusively by other processes like CICS.