Restrictions when creating or working with distributed files with DB2^® Multisystem

 

You need to be aware of some restrictions when creating or working with distributed files.

The restrictions are as follows:

• First-change first-out (FCFO) access paths cannot be used because the access paths are partitioned across multiple nodes.

• A distributed file can have a maximum of one member.

• A distributed file is not allowed in a temporary library (QTEMP).

• Data in the partitioning key has a limited update capability. Generally, when choosing a partitioning key, you should choose fields whose values do not get updated. Updates to the partitioning key are allowed as long as the update does not cause the record to be partitioned to a different node.

• Date, time, timestamp, or floating-point numeric fields cannot be used in the partitioning key.

• Source physical files are not supported.

• Externally described files are supported for distributed files; program-described files are not supported.

• If the access path is unique, the partitioning key must be a subset of the unique key access path.

• Constraints are supported, and referential constraints are supported only if the node group of both the parent and foreign key files are identical and all of the fields of the partitioning key are included in the constraint. The partitioning key must be a subset of the constraint fields. Also, for unique and primary constraints, if the access path is unique, the partitioning key must be a subset of the unique key access path.

• On the CRTPF command, the system parameter must have the value *LCL specified (CRTPF SYSTEM(*LCL)). SYSTEM(*RMT) is not allowed.

• Any time a logical file is created over a distributed file, the logical file also becomes distributed, which means that you cannot build a local logical file over just one piece of the physical file on a specific node. SQL views are the exception to this, if the view is a join and if all of the underlying physical files do not have the same node group. In this case, the view is only created on the local system. Even though this view is not distributed, if you query the view, data is retrieved from all of the nodes, not just from the node where the view was created.

  Join files can only be created using SQL.

  For DDS-created logical files, only one based-on file is allowed.

• Coded character set identifiers (CCSIDs) and sort sequence (SRTSEQ) tables are resolved from the originating system.

• Variable-length record (VLR) processing is not supported. This does not mean that variable-length fields are not supported for distributed files. This restriction only refers to languages and applications that request VLR processing when a file is opened.

• End-of-file delay (EOFDLY) processing is not supported.

• Data File Utility (DFU) does not work against distributed files, because DFU uses relative record number processing to access records.

• A distributed file cannot be created into a library located on an independent auxiliary storage pool (IASP).

 

Parent topic:

Create Physical File command and SQL CREATE TABLE statement