z/TPF Program Management - IBM

Alternate FCTB loader benefits
Use the alternate FACE table (FCTB) loader to perform the following tasks:
v Modify your database without a scheduled outage. This includes:
– Removing deactivated pool extents
– Expanding the number of tracks and cylinders
– Removing or reduce the number of ordinals in fixed file records
– Changing the physical location of records types
– Changing the file address reference format (FARF) address for fixed-file
records.
Attention: Do not use the alternate FCTB loader to modify records that are
critical to the z/TPF system or unexpected results can occur.
See “Alternate FCTB compatibility checking” on page 31 and Table 2 on page 31
for more information about using an alternate FCTB.
v Activate an alternate FCTB on all processors or any specific processor.
v Use the ufct.c user exit to customize compatibility checking for the alternate
FCTB and the existing database. See “Alternate FCTB compatibility checking” on
page 31 for more information about how to ensure that a valid alternate FCTB is
loaded.
v Use the uftz.c user exit to maintain a log of alternate FCTB activity.
Alternate FCTB loader programming considerations
The following lists the programming considerations for the alternate FACE table
(FCTB) loader:
30 z/TPF Program Management
v A maximum of one alternate FCTB and one base FCTB can be loaded for each
z/TPF image.
v If you use the ZFCTB ACCEPT command to accept an alternate FCTB that is
active, that alternate FCTB becomes the base FCTB; no other FCTB exists.
v You must delete or accept the existing alternate FCTB to load another alternate
FCTB.
v The FCTBCLEAR parameter on the @DEFINE control statement specifies if an
existing alternate FCTB on a z/TPF image is cleared or left intact when an initial
program load (IPL) is performed on the z/TPF image. See z/TPF Program
Management for more information about the FCTBCLEAR parameter on the
@DEFINE control statement.
v You can display the status of an alternate FCTB by using the ZIMAG DISPLAY
IMAGE command. See z/TPF Operations for more information about the ZIMAG
DISPLAY IMAGE command and displaying the status of an alternate FCTB.
v If you perform a hard IPL and an active alternate FCTB exists, you will be
prompted in the IPLB program to specify the base FCTB or the alternate FCTB.
If the base FCTB is specified, the alternate FCTB is deactivated. This allows you
to prevent looping errors that result from an alternate FCTB that is not valid.
When a soft IPL is performed, this option is not available.
v The offline loader (TPFLDR) creates the input medium that contains the alternate
FCTB used by the ZFCTB LOAD command. If there are items on the input
medium other than an FCTB, the ZFCTB LOAD command is rejected.
v The alternate FCTB loader is not supported from image 1 to prevent interference
with the general file loader. See z/TPF Program Management for more
information about the general file loader.