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 Transparencydoes 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=Toption 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 activeDatacom VSAM Transparencyfile. This restriction applies to any invocation of CEMT OPEN or CLOSE, not just the invocation from an application program.Issuing CEMT OPEN to an activeDatacom VSAM Transparencyfile causes the file to be markedclosedin CICS.
- Issuing command levelEXEC CICS SET OPENorEXEC CICS SET CLOSEalways returns INVALID REQUEST.
- Issuing command levelEXEC CICS SET OPENorEXEC CICS SET CLOSEwith anEMPTYoption 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=LSRin ACB) or Global shared resources (MACRF=GSRin ACB).
- Access type/processing mode combinations are designated in the following table:VSAM Access TypesSequential VSAM Processing ModeSkip Sequential VSAM Processing ModeDirect VSAM Processing ModeKeyedSupportedSupportedSupportedAddressedSupportedNot applicableUnsupportedControl IntervalUnsupportedAny request to add, delete, or update a Control Interval is unsupported. Only read requests are supported.Not applicableUnsupported
- 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 theDatacom VSAM Transparencyfile by the end of a job, the job ends abnormally. If a transaction backout is requested,Datacom/DBbacks out updates to the converted table.
- Multiple z/OS subtasks accessingDatacom VSAM Transparencyfiles concurrently from the same address space:Datacom VSAM Transparencyrequests may be issued from a single z/OS subtask, but not concurrently from more than one.
- TCLOSE request.
- Write buffer commands.
- AccessingDatacom VSAM Transparencyusing the IDCAMS utility.
Batch Operating Restrictions
Consider the following batch operating restrictions:
- Batch applications must name the same batch VSAM Interface Table (VIT) for allDatacom VSAM Transparencyfiles within a jobstep.
- COBOL applications using OPEN OUTPUT must codeREUSE=YESin 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 Transparencydoes 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 multipleDatacom/DBtables, 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 ofDatacom/DBtables. However, you can create SQL views that are used by nontransparency applications against any fixed-length tables otherwise used by the transparency.
- Datacom/DBtables 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 sameDatacom/DBtable. No table joins are permitted to formulate the VSAM record image.
- Using SQL statements to defineDatacom/DBtables 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, useDatacom Datadictionaryto 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
DADS Plus
ConsiderationsIf 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.