Restrictions and Considerations

Learn about Datacom VSAM Transparency restrictions and considerations, such as unsupported functions, program restrictions for batch and online, VSAM files, online URT, and SQL.

Unsupported Functions

Datacom VSAM Transparency
ignores the following features when invoked by user programs:
  • VSAM password processing
  • Unsupported exits:
    • JRNAD (journaling exit)
    • UPAD (user exit)
  • Datacom VSAM Transparency
    does not report the following SHOWCB and TESTCB accurately:
    • AVSPAC
    • BUFND
    • BUFNI
    • BUFNO
    • BUFSP
    • CATALOG
    • CRA
    • ENDRBA
    • FS
    • MAREA
    • MLEN
    • NCIS
    • NDELR
    • NEXCP
    • NINSR
    • NIXL
    • NLOGR
    • NRETR
    • NSSS
    • NUPDR
    • STMST
    • STRMAX
    • STRNO
  • TYPE=
    T
    option of the CLOSE request

Batch and Online Program Restrictions

Batch and online programs that
cannot
be executed under
Datacom VSAM Transparency
include the ones that use one or more of the following functions:
  • VSAM Catalog operations.
  • Separate processing at the Index level or Data Component level.
  • Processing of an alternate index as a separate data set, that is, the ACB specification MACRF=AIX.

Online Only Program Restrictions

Online programs that
cannot
be executed under
Datacom VSAM Transparency
include the ones that use one or more of the following functions:
  • Indirect access.
  • Issuing the CICS commands, CEMT OPEN, or CLOSE to an active
    Datacom VSAM Transparency
    file. This restriction applies to any invocation of CEMT OPEN or CLOSE, not just the invocation from an application program.
    Issuing CEMT OPEN to an active
    Datacom VSAM Transparency
    file causes the file to be marked
    closed
    in CICS.
  • Issuing command level
    EXEC CICS SET OPEN
    or
    EXEC CICS SET CLOSE
    always returns INVALID REQUEST.
  • Issuing command level
    EXEC CICS SET OPEN
    or
    EXEC CICS SET CLOSE
    with an
    EMPTY
    option with the intent to RESET the reusable file.

Batch Only Program Restrictions

Batch programs that
cannot
be executed under
Datacom VSAM Transparency
include the ones that use one or more of the following functions:
  • VSAM requests initiated from the IBM ISAM interface facility, IBM SAM interface to VSAM, or other similar interfaces.
  • Checkpointing.
  • Local shared resources (
    MACRF=
    LSR
    in ACB) or Global shared resources (
    MACRF=
    GSR
    in ACB).
  • Access type/processing mode combinations are designated in the following table:
    VSAM Access Types
    Sequential VSAM Processing Mode
    Skip Sequential VSAM Processing Mode
    Direct VSAM Processing Mode
    Keyed
    Supported
    Supported
    Supported
    Addressed
    Supported
    Not applicable
    Unsupported
    Control Interval
    Unsupported
    Any request to add, delete, or update a Control Interval is unsupported. Only read requests are supported.
    Not applicable
    Unsupported
  • Restrictions to GETIT processing in update mode:
    • If GETIT for update is active on a file, the file cannot be opened for update using another ACB.
    • If a file is open for update in non-GETIT mode, the file can be opened for update using another ACB but it is not granted the GETIT resource.
  • Backward processing is not supported with WF2 access.
  • Failure to issue a CLOSE request by the end of a job. If the program does not explicitly issue a CLOSE for the
    Datacom VSAM Transparency
    file by the end of a job, the job ends abnormally. If a transaction backout is requested,
    Datacom/DB
    backs out updates to the converted table.
  • Multiple z/OS subtasks accessing
    Datacom VSAM Transparency
    files concurrently from the same address space:
    Datacom VSAM Transparency
    requests may be issued from a single z/OS subtask, but not concurrently from more than one.
  • TCLOSE request.
  • Write buffer commands.
  • Accessing
    Datacom VSAM Transparency
    using the IDCAMS utility.

Batch Operating Restrictions

Consider the following batch operating restrictions:
  • Batch applications must name the same batch VSAM Interface Table (VIT) for all
    Datacom VSAM Transparency
    files within a jobstep.
  • COBOL applications using OPEN OUTPUT must code
    REUSE=
    YES
    in the batch VIT.

VSAM File Restrictions

Restrictions on VSAM files to convert are as follows:
  • To be eligible for conversion, the VSAM file must be a Key-Sequenced Data Set (KSDS), that is,
    Datacom VSAM Transparency
    does not support the following VSAM data set types:
    • Relative Record Data Set (RRDS)
    • Entry-Sequenced Data Set (ESDS)
    • Segmented records in CICS
  • To be eligible for conversion, the record length of the VSAM file cannot exceed 32767 bytes.

Online URT Restrictions

MDB-related tables are tables that are converted from the same source VSAM file. The following restrictions apply to the definition of MDB-related tables in online URTs:
  • Splitting the definitions of MDB-related tables between two or more URTs is not supported. When a VSAM file is converted to multiple
    Datacom/DB
    tables, all of the related tables must be defined to the same URT.
  • Using a higher numbered URT for defining MDB-related tables than for defining unrelated tables from the same database is not supported. If you define unrelated tables in different URTs than you define MDB-related tables from the same database, define the unrelated tables in higher-numbered URTs than the URT used for defining the MDB-related tables.
To avoid the impact of these restrictions, define all tables residing in the same DBID to the same URT.

SQL Restrictions

If you use the SQL option of
Datacom/DB
consider the following SQL-related restrictions pertaining to the use of the
Datacom VSAM Transparency
product:
  • SQL views are not supported for the transparency's perception of
    Datacom/DB
    tables. However, you can create SQL views that are used by nontransparency applications against any fixed-length tables otherwise used by the transparency.
  • Datacom/DB
    tables that are defined as variable-length tables (those with user compression exit DBVVRPR) are not accessible using SQL.
  • All elements necessary to construct a single VSAM record image must come from the same
    Datacom/DB
    table. No table joins are permitted to formulate the VSAM record image.
  • Using SQL statements to define
    Datacom/DB
    tables that are designed to be included in an MDB structure is not fully supported. Using SQL commands to define tables results in nonshared keys. To meet requirements for MDB keys, use
    Datacom Datadictionary
    to alter the key name (DATACOM-NAME) and key-ID (DATACOM-ID) generated by an SQL definition.
  • SQL null fields are not supported within the elements that are used to construct the VSAM record image.

DADS Plus
Considerations

If you are using
DADS Plus
, remove any
Datacom VSAM Transparency
files under the control of
DADS Plus
from the
DADS Plus
control list. Do not attempt to place
Datacom VSAM Transparency
files under the control of
DADS Plus
.
If you use EXCP for the data area,
Datacom
encryption can only be used for fixed length files.
If you decide in the future to migrate from EXCP to VSAM linear data sets, you must remove DB encryption before you can start that migration.
If you want to use encryption, the current best practice is to use Pervavisive Encyrption offered via VSAM linear data sets.