To use SDT support, you must perform the
following tasks. Some of them will already have been done for an installation
that currently uses function shipping and/or data tables.
- Either ensure that the following modules are in an authorized system library
in the LNKLST of the MVS™ system, or move them into a library in the LPALST concatenation.
- DFHDTSVC and DFHDTCV, because all regions using shared data tables must
use the same level of SVC code.
- DFHMVRMS, the RESMGR exit stub, because CICS® JOBLIB/STEPLIB data sets are unavailable
at end-of-memory.
The following modules are placed by the installation of CICS into the
target library SDFHLINK, which is normally included in the LNKLST concatenation.
- If SDFHLINK is in the LNKLST concatenation, you should issue the operator
command MODIFY LLA,REFRESH and wait for the confirmatory message CSV210I LIBRARY LOOKASIDE REFRESHED in order to make the modules available.
- If SDFHLINK is not in the LNKLST concatenation, you should either copy
the modules into a suitable library that is included and issue an LLA refresh,
or copy the modules into a library in the LPALST concatenation and re-IPL
the MVS system specifying CLPA.
- If any files in any AOR are to exploit sharing, make sure that CICS is
defined as an MVS subsystem.
- Define security authorization so that FORs can act as SDT servers and
AORs can access files owned by servers, depending on the level of security
required. In a single MVS image:
- Any number of FORs can act as SDT servers
- A single AOR can use any number of these FORs
- A single FOR can serve any number of AORs
- A region can act as an AOR for one data table and as an FOR for a different
data table.
- If two FORs should have the same APPLID, at any given time SDT ensures
that only one of these FORs is used as an SDT server. However, there is nothing
to prevent one FOR acting as an SDT server and another FOR, with the same
APPLID, being used for function shipped requests. You should check that your
operational procedures do not allow this because there is a risk that data
table requests that use SDT services are not directed to the same region as
requests that use function shipping.
- Define those files in the FOR that are data tables as either CICS-maintained data tables or user-maintained data tables.
- Create additional remote file definitions in the AOR if required. No changes
are needed to existing remote file definitions.
- For any AOR that is to share data tables, specify ISC=YES as a system
initialization parameter and define MRO or ISC links to the relevant FORs.
- Before using shared data tables you might need to change some of your
JCL statements, modify your operational procedures, or increase the value
of the MAXUSER MVS initialization parameter. For more information, see MVS JCL requirements when using shared data tables.
Table 2 shows the load modules to be installed
in your CICS system in order to use SDT.
Table 2. Load modules in SDT
Load module |
Load library |
How loaded |
Description |
DFHDTINS |
SDFHLOAD |
CICS load above the 16MB line |
Initialization |
DFHDTSVC |
SDFHLINK |
MVS LOAD above the 16MB line from link-list |
Performs all functions that need MVS authorization |
DFHDTFOR |
SDFHAUTH |
MVS LOAD above the 16MB line |
Data table FOR module |
DFHDTAM |
SDFHAUTH |
MVS LOAD into subpool 252 storage above the 16MB line |
Data table access manager. It includes code that is executed
in cross-memory mode from an AOR |
DFHDTAOR |
SDFHAUTH |
MVS LOAD above the 16MB line |
Data table AOR module |
DFHDTCV |
SDFHLINK |
MVS LOAD into ECSA from link-list |
Connection validation (AOR) |
DFHDTXS |
SDFHAUTH |
MVS LOAD into ECSA |
Connection security checking (FOR) |
DFHMVRMS |
SDFHLINK |
MVS LOAD above the 16MB line from link-list |
Resource manager EOT/EOM interface code |
Storage occupancy
The total size of the modules that occupy storage above the 16MB line is
about 41KB. For modules that are in ECSA storage, about 1.5KB are required
for each logged-on FOR, and about 0.5KB for each AOR.
The modules are all eligible for inclusion in the link pack area (LPA),
but only DFHDTFOR, DFHDTAM, DFHDTAOR, and possibly DFHDTCV are used sufficiently
frequently to be worth considering.
[[ Contents Previous Page | Next Page Index ]]