Version 7.4.4

Device and File Considerations

This section provides information for the following device and system file related topics:


FBA Devices

All device definitions for Adabas control statements for FBA disks should specify one of the following devices types:

Note:
Virtual FBA devices are not permanent and are, therefore, only suitable for holding temporary or work data sets.

Choose a device type based on the block sizes given in the following tables:

SCSI Device Types:

Dev Type Asso blksz Data blksz Work blksz Temp blksz Sort blksz PLOG blksz CLOG blksz
5512 2048 4096 4096 4096 4096 4096 4096
6512 4096 8192 8192 8192 8192 8192 8192
7512 4096 16384 16384 16384 16384 16384 16384

Virtual FBA Device Types:

Dev Type Asso blksz Data blksz Work blksz Temp blksz Sort blksz PLOG blksz CLOG blksz
5121 2048 4096 4096 4096 4096 4096 4096
5122 4096 8192 8192 8192 8192 8192 8192
5123 4096 16384 16384 16384 16384 16384 16384

The pseudo-cylinder for each of these devices has a different number of blocks as described below:

5512 cylinder = FBA blocks/1024
6512 cylinder = FBA blocks/1024
7512 cylinder = FBA blocks/1024
5121 cylinder = FBA blocks/960
5122 cylinder = FBA blocks/960
5123 cylinder = FBA blocks/960

The size definitions for FBA devices on Adabas control statements can specify the number of pseudo-cylinders or the number of Adabas blocks (RABNs).

Make sure that the number of FBA blocks in the minidisk is a multiple of the pseudo-cylinders listed above. In addition, the minidisk size must be one pseudo-cylinder larger than the size specified in the Adabas size definitions:

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Adding New Devices

Support for new device types that include user-defined block sizes can be implemented in Adabas by modifying one of the table of device-constant entries (TDCEs) reserved for this purpose. A TDCE is X’40’ bytes long and the first free TDCE can be identified by X’0000’ in its first two bytes (TDCDT).

Under z/VM for all versions of Adabas prior to Version 6.2, the address of the first TDCE is at offset ADAIOR+ X‘34’.

For Adabas Version 6.2 and 7.1, TDCE entries are in the ADAIOR CSECT TDCON: the first TDCE entry is at offset 0; the first free TDCE entry is at offset X‘680’.

This information is valuable when adding an additional TDCE entry.

The ADDEVICE EXEC distributed on the release tape can be used to add new device types. This EXEC creates zap files called USERDEVn ZAP to modify the TDCEs. It also modifies the table of valid device names DEVICE TABLE and the USERDEV TABLE. These tables are used for verification during the online installation procedure.

Information to be Zapped into the First Free TDCE

The information in the following tables must be zapped into the first free TDCE. The rules described in the section General Rules for Defining Device Block Sizes must be followed when changing the TDCE.

Label Offset Contents
TDCDT 00 Device type in unsigned decimal (X’3385’), must be numeric, and unique among all TDCEs
TDCKSN 02 Constant set number: must be uniquely chosen from the values X’28’ (reserved for BS2000 device type 2006), X’2B’, or X’2E’
TDCF 03 The flag bit must be set—TDCFFBA (X’80’) for FBA/PAM devices or TDCFCKD (X’40’) for CKD devices
TDCDT1 04 see note below
TDCDT2 05 see note below
TDCDT3 06 see note below
TDCDT4 07 see note below
TDCMSBS 08 Refer to the TDCMSBS default table in appendix A in Maximum Sequential Block Size in the Adabas z/OS installation instructions for more system and device related information.
TDCTPC 0A Number of tracks per cylinder
TDCCIPT 0C Number of FBA blocks or PAM pages per track (if TDCFFBA is set). For BS2000 less than or equal to 16.
TDCBPCI 0E Number of bytes per FBA block or PAM page (2048 if TDCFFBA is set)
TDCABPT 10 Number of Associator blocks per track
TDCABS 12 Associator block size
TDCACPB 14 Number of FBA blocks or PAM pages per Associator block (if TDCFFBA is set)
TDCDBPT 16 Number of Data Storage blocks per track
TDCDBS 18 Data Storage block size
TDCDCPB 1A Number of FBA blocks or PAM pages per Data Storage block (if TDCFFBA is set)
TDCWBPT 1C Number of Work blocks per track
TDCWBS 1E Work block size
TDCWCPB 20 Number of FBA blocks or PAM pages per Work block (if TDCFFBA is set)
TDCTSBPT 22 Number of TEMP or SORT blocks per track (if TDCFFBA is set)
TDCTSBS 24 TEMP or SORT block size
TDCTSCPB 26 Number of FBA blocks or PAM pages per TEMP or SORT block (if TDCFFBA is set)
TDCPBPT 28 Number of PLOG blocks per track
TDCPBS 2A PLOG block size
TDCPCPB 2C Number of FBA blocks or PAM pages per PLOG block (if TDCFFBA is set)
TDCCBPT 2E Number of CLOG blocks per track
TDCCBS 30 CLOG block size
TDCCCPB 32 Number of FBA blocks or PAM pages per CLOG block (if TDCFFBA is set)

Note:
One or more z/VM codes for identifying the device type: the UCB unit type from UCBTBYT4.

In addition, the length of a sequential protection log block may have to be increased. Under z/VM, this length is contained in the corresponding PTT entry in CSECT I_PTT of the load module ADAIOR. The address of the first PTT entry is contained in the fullword at ADAIOR+X‘4C8’. PTT entries begin at offset 0 into CSECT I_PTT.

Each PTT entry is X’10’ bytes long and has the structure shown below:

Label Offset Contents
PTTPN 00 Program number
PTTFT 01 File type
PTTN 02 DD name characters 2 - 8
PTTF 08 Flags:
OUT (X’80’) output
BSAM (X’40’) BSAM
BACK (X’20’) read backwards
JCL (X’10’) BLKSIZE/LRECL/RECFM taken from DATADEF statement or label
UNDEF (X’04’) undefined record format
VAR (X’02’) variable record format
                                                     
- 09 Reserved
PTTMBS 0A Maximum block size
- 0C Reserved

The PTT entry for the sequential protection log can be identified by X‘12F1’ in its first two bytes.

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General Rules for Defining Device Block Sizes

The following general rules must be followed when defining Adabas device block sizes:

Block Rules for ASSO/DATA

The following rules apply for Associator and Data Storage blocks:

Block Rule for WORK

The Work block size must be greater than either (maximum compressed record length + 110) or (Associator block size + 110), whichever is greater.

Block Rules for TEMP/SORT

If ADAM direct addressing is used:

size > (maximum compressed record length + ADAM record length + 24);
size > 277 (maximum descriptor length + 24)

However, TEMP and SORT are generally read and written sequentially; therefore, the larger the TEMP/SORT block size, the better.

Block size for TEMP and SORT must be greater than the block size for Data Storage.

Block Rule for PLOG or SIBA

The following rules apply for PLOG or SIBA blocks:

The block size (BLKSIZE) of a sequential file is determined as follows:

if PTTF(JCL) then BLKSIZE is taken from file assignment statement or label;
if PTTMBS > 0 then BLKSIZE = PTTMBS;
if PTTMBS = 0 then
if tape then BLKSIZE = 32760;
else BLKSIZE = TDCMSBS;
else if BLKSIZE in file assignment statement or label then use it;
if PTTF(OUT) then
if QBLKSIZE > 0 then BLKSIZE = QBLKSIZE;
if tape then BLKSIZE = 32760;
else BLKSIZE = TDCMSBS;
else error.

Note:
QBLKSIZE is an ADARUN parameter.

Using 3480/3490 Tape Cartridge Compression (IDRC)

The use of hardware compression (IDRC) is not recommended for protection log files. The ADARES BACKOUT function will run much longer when processing compressed data. Also, the BACKOUT function is not supported for compressed data on z/VM systems.

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