Version 7.4.4

Device And File Considerations

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 BS2000, the address of the first TDCE is at offset ADAIOR+ X‘34’ for all versions of Adabas.

Adabas direct access datasets are always mapped to UPAM files, removing the need to consider physical device characteristics. PAM pages in a dataset are addressed relative to the dataset beginning.

Adabas blocks comprise one or more PAM pages. An Adabas virtual track is made up of a fixed number of blocks, and an Adabas virtual cylinder comprises a fixed number of tracks. The definition of tracks and cylinders are independent of the physical device.

There are a number of predefined virtual devices for BS2000 that should meet most of the storage capacity needs that arise. It should be noted that the virtual memory requirement increases significantly with a larger block size.

Support for new device types, including user-defined block sizes, can be implemented in ADAIOR by modifying one of the TDCEs reserved for this purpose.


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 Set to zero under BS2000
TDCDT2 05 Set to zero under BS2000
TDCDT3 06 Set to zero under BS2000
TDCDT4 07 Set to zero under BS2000
TDCMSBS 08 In BS2000, 32760 for compatibility. Refer to the TDCMSBS default table 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
TDCCCPB2 32 Number of FBA blocks or PAM pages per CLOG block (if TDCFFBA is set)

In addition, the length of a sequential protection log block may have to be increased. This length is contained in the corresponding PTT entry in CSECT ADAIOI of the load module ADAIOI. The address of the first PTT entry is contained in the fullword at ADAIOI+X‘E4’.

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.

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Device Types and Block Sizes

The primary access method for direct access datasets used by Adabas under BS2000 is PAM (primary access method). The device types defined by Adabas establish a logical structure on a PAM dataset in order to process a fixed number of consecutive PAM blocks (e.g., one Adabas block consisting of two PAM blocks or one logical track consisting of four PAM blocks).

These device types are “artificial”; there is no relation to the physical devices being used. A maximum of 16 PAM blocks per track can be combined into one I/O call. For more than 16 PAM blocks per track, parameter chaining is used.

The artificial device types defined by Software AG for BS2000 systems are summarized in the following table. The ASSO, DATA, WORK, PLOG, CLOG, and TEMP/SORT/DSIM block sizes are given in RABNs per track.

Device Trks/Cyl PAM Blks/Trk ASSO DATA WORK PLOG CLOG TEMP/SORT/DSIM Notes
2000 20 4 2048:4 4080:2 4096:2 4096:2 4096:2 4080:2  
2001 19 8 2044:8 4092:4 4096:4 4096:4 8192:2 8192:2  
2002 19 8 4092:4 8188:2 8192:2 8192:2 16384:1 16384:1 see note 1
2003 17 15 2044:15 6140:5 6144:5 6144:5 10240:3 10240:3  
2004 17 15 6140:5 10236:3 10240:3 10240:3 30720:1 30720:1  
2005 11 20 2044:20 4092:10 8192:5 8192:5 10240:4 10240:4  
2006 11 20 4092:10 8188:5 10240:4 10240:4 10240:4 10240:4  
2007 17 15 10236:3 30716:3 30720:3 30720:3 30720:3 30720:3 see note 2
2008 17 16 4092:8 32656:1 32760:1 32760:1 32760:1 32760:1 see note 1
2009 17 16 4092:8 32656:1 32740:1 32740:1 32740:1 32740:1  
2010 15 16 4092:8 8188:4 16380:2 16380:2 16380:2 16380:2 see note 1
2200 15 16 4092:8 8088:4 16380:2 16380:2 16380:2 16380:2 see note 1
2201 15 12 4092:6 12184:2 12288:2 12288:2 12288:2 12288:2 see note 1
2202 15 16 4092:8 16280:2 16380:2 16380:2 16380:2 16380:2 see note 1

Notes:

  1. This device can be used with BS2000/NK4 disk types. In these cases, all direct access database files have been defined with a standard block size which is a multiple of 2.
  2. Although supported, the 2007 device is not recommended for use with Adabas. Support for the 2007 will be removed in a later Adabas release.

If the current database device is not of a compatible type for NK4 disks and it is necessary to migrate it to those disks, you must use the ADAORD RESTRUCTUREDB utility as described in Adabas Utilities.

Splitting Datasets Across Volumes

For private volumes, splitting is possible under every LOGON user ID:

In ISP format:

/FILE dataset,DEVICE=D3480,VOLUME=PRIV01,SPACE=60000
/FILE dataset,DEVICE=D3480,VOLUME=PRIV02,SPACE=60000

In SDF format:

/CREATE-FILE dataset,PRIV-DISK(SPACE=(60000),VOLUME=PRIV01)
/MOD-FILE-ATTR dataset,PROT=(USER-ACC=*ALL)
/MOD-FILE-ATTR dataset,SUP=PRIV-DISK(SPACE=(60000),VOLUME=PRIV02)

For public volumes, the splitting is possible under every LOGON user ID if the master catalog entry of the pubset has the attribute:

PHYSICAL-ALLOCATION=USER-ALLOWED

This attribute is set by issuing the following command under TSOS:

/MOD-MASTER-CAT CAT-ID=ABC,PHYSICAL-ALLOCATION=USER-ALLOWED

Once this attribute is set, it is possible to split a dataset across two or more public volumes under any LOGON user ID that has the right of space allocation on that particular pubset.

In ISP format:

/FILE dataset,VOLUME=ABC.00,DEVICE=D3480,SPACE=60000
/FILE dataset,VOLUME=ABC.01,DEVICE=D3480,SPACE=60000

In SDF format:

/CREATE-FILE dataset,PUB(SPACE=(60000),VOLUME=ABC.00)
/MOD-FILE-ATTR dataset,PROT=(USER-ACC=*ALL)
/MOD-FILE-ATTR dataset,SUP=PUB(SPACE=(60000),VOLUME=ABC.01)

At this point, even a particular physical allocation can be made.

In ISP format:

/FILE dataset,VOLUME=ABC.02,DEVICE=D3480,SPACE=(20002,60000,ABS)

In SDF format (following the CREATE-FILE and MOD-FILE_ATTR...PROT specifications listed earlier):

/MOD-FILE-ATTR dataset,SUP=PUB(SPACE=ABSOLUTE(20002,60000),VOLUME=ABC.02)

The example extent covers physical PAM pages 20002 through 80001 on volume ABC.02. The required disk space must, of course, be available. If you are unsure of the available disk space, consult your system administrator.

Saving the Extent List of Datasets

The utility ADAR2E converts the extent list of given datasets into a JOB containing /CREATE-FILE commands. For more information, see the section on the ADAR2E utility in the Adabas Utilities documentation.

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