Execution data sets

ACBLIB data sets

In systems that share data, the ACBLIBs in both systems must be identical, or the systems must share the same ACBLIB.

DBDLIB data set

The IMS.DBDLIB data set contains the database description blocks (DBDs) that are created by the Database Description Generation (DBDGEN) utility.

DBRC RECON data sets

FORMAT data sets

IMS.REFERAL,IMS.FORMAT, and IMS.TFORMAT are initialized during stage 2 of IMS system definition. IMS.FORMATA and IMS.FORMATB are created by copying the staging library, IMS.FORMAT. You must allocate one additional track for each user-defined format/message descriptor set for the IMS.FORMAT, IMS.REFERAL, and IMS.TFORMAT data sets.

Log data sets

Message queue data sets

MSDB data sets

Online change data sets

PGMLIB data sets

The IMS.PGMLIB data set contains user-written application programs. This dataset can be a PDS or a PDSE.

PSBLIB data sets

The IMS.PSBLIB data set contains the program specification blocks (PSBs) created by the Program Specification Block Generation (PSBGEN) utility.

SYSOUT data sets

Trace data sets

IMS.ACBLIB

ACBLIB contains the application control blocks (ACBs) that are created by the Application Control Blocks Maintenance (ACBGEN) utility. Its contents are copied by the Online Change Copy utility to either the IMS.ACBLIBA data set or the IMS.ACBLIBB data set.

IMS.ACBLIBA, IMS.ACBLIBB

ACBLIBA and ACBLIBB contain ACBLIB members. When one of these libraries is active (in use by the online system), the contents of IMS.ACBLIB are copied to the other, or inactive, library for use in the next online change run.

IMS.ACBLIBA or IMS.ACBLIBB can be brought online by a sequence of master terminal operator /MODIFY commands.

If you specify DOPT in the APPLCTN macro, concatenate the library that contains these PSBs after the library that contains the non-DOPT PSBs (that is, after the library pointed to by the IMS.ACBLIBA or IMS.ACBLIBB DD statements). The order of concatenation must be the same for the IMS.ACBLIBA and IMS.ACBLIBB data sets.

IMS.DBDLIB

DBDLIB contains the database description blocks (DBDs) that are created by the Database Description Generation (DBDGEN) utility. Each DBD (one per database) requires approximately 1500 bytes to 2500 bytes of direct-access storage. Exact requirements depend on the number of data set groups, segments, fields, and hierarchic levels.

IMS.DFSOLPnn, v.DFSOLSnn

DFSOLPnn and DFSOLSnn are the online log data sets (OLDS) that are used by the IMS online systems. OLDSs can occur singly (SNGL) or in pairs (DUAL). DFSOLPnn is the primary (or SNGL) OLDS. DFSOLSnn is the secondary OLDS. The nn suffix can range from 00 to 99. A minimum of 3 OLDSs (SNGL or DUAL) must be available to start IMS. The OLDSs do not support compression.

IMS.DFSTRA01, IMS.DFSTRA02

DFSTRA01 and DFSTRA02 are the external trace data sets that are used by the IMS online systems. The two data sets are used when the trace table OUT parameter is used in the DFSVSMxx OPTIONS statement or when the /TRACE SET ON TABLE nnn OPTION LOG command is used. When DFSTRA01 fills, DFSTRA02 is used; when DFSTRA02 fills, DFSTRA01 is used.

IMS.DFSTRA0T

If you use tape for the external trace data set, you must use DFSTRA0T instead of DFSTRA01 and DFSTRA02.

DFSTRA0T must be dynamically allocated.

IMS.DFSWADSn

DFSWADSn are the write-ahead data sets (WADS) used by the IMS online systems. WADS can occur singly (SNGL) or in pairs (DUAL), but primary or secondary concepts do not apply as they do with OLDS. The n suffix can range from 0 to 9. To start IMS, a minimum of 1 WADS must be available.

IMS.FORMAT

FORMAT contains the Message Format Service (MFS) blocks created by the MFS Language utility. Its contents are copied by the Online Change Utility to either IMS.FORMATA or IMS.FORMATB.

IMS.FORMATA, IMS.FORMATB

FORMATA and FORMATB contain FORMAT members. When one of these libraries is active (in use by the online system), the contents of IMS.FORMAT are copied to the other, or inactive, library for use in the next online change run.

IMS.FORMATA or IMS.FORMATB can be brought online by a sequence of master terminal operator /MODIFY commands.

IMS.IEFRDER, IMS.IEFRDER2

IEFRDER typically refers to the primary IMS batch log. IEFRDER2 typically refers to the secondary IMS batch log. They can also refer to the input data set in the IMSRDR procedure.

IMS.IMSDALIB

IMSDALIB defines the non-authorized partitioned data set (PDS) in which members to be dynamically allocated can be stored. Examples include RECON definitions, database definitions, and anything that is in a DFSMDA member.

IMS.IMSMON

IMSMON contains the trace records for either the DB Monitor or IMS (System) Monitor if the trace records are not routed to the IMS log.

IMS.MODSTAT

This data set is a single-record BSAM data set and requires one track of storage.

Before the IMS system can be run, you need to initialize IMS.MODSTAT.

IMS.MODSTAT2

MODSTAT2 is used only in an XRF complex; this data set is identical in function to IMS.MODSTAT. Its ddname must be MODSTAT2. As with MODSTAT, you need to initialize this data set before the IMS system can run.

IMS.MSDBCP1, IMS.MSDBCP2

MSDBCP1 and MSDBCP2 are required if MSDBs are defined to the system. During each IMS checkpoint, a control record followed by the contents of the contiguous block of virtual storage occupied by the MSDBs is written to one of these data sets. The data sets are used alternately by successive checkpoints, with each subsequent checkpoint overlaying a previous one.

IMS.MSDBCP3, IMS.MSDBCP4

MSDBCP3 and MSDBCP4 are used only in an XRF complex; these data sets are identical in function to MSDBCP1 and MSDBCP2. With XRF, any two of the four data sets can contain the latest MSDB checkpoint. Although an active subsystem can select the data set containing the latest MSDB checkpoint and any other, the alternate subsystem must select the two data sets not used by the active subsystem.

IMS.MSDBDUMP

MSDBDUMP is required when the command /DBDUMP specifies database MSDB. This command causes a dump of all MSDBs to be written to this data set. The contents are identical to that of MSDBCPx. Successive executions of the command cause the previous contents to be overlaid.

IMS.MSDBINIT

MSDBINIT is required for an IMS system that includes MSDBs. This data set contains a record for each MSDB segment. It is read during all cold starts and during a normal restart if the MSDBLOAD parameter is specified for the /NRESTART command. It is produced by executing the MSDB Dump Recovery or MSDB Maintenance utility. MSDBINIT can contain one, several, or all MSDBs defined.

IMS.PGMLIB

PGMLIB contains user-written application programs.

IMSPLEX.OLCSTAT

OLCSTAT is an optional data set that contains global online change information and status. OLCSTAT is a global data set that is dynamically allocated by IMS. The MODSTAT and MODSTAT2 data sets do not need to be defined in the IMS control region JCL when OLCSTAT is used.

To enable global online change, OLCSTAT must be defined instead of the local MODSTAT data set. All IMS systems in an IMSplex must define the same physical OLCSTAT data set. Otherwise, IMS initialization fails. OLCSTAT is required if OLC=GLOBAL is defined.

To initialize the OLCSTAT data set, run the Global Online Change utility, DFSUOLC0.

IMS.PSBLIB

PSBLIB contains the program specification blocks (PSBs) created by the PSBGEN utility. Each PSB (one per program) requires approximately 250 bytes to 500 bytes of direct-access storage. Exact requirements depend on the number of I/O PCBs and databases (PCBs) in the PSB and the number of sensitive segments. This data set is required in DB and DB/DC systems.

IMS.QBLKS, IMS.SHMSG/1-9, IMS.LGMSG/1-9

QBLKS, SHMSG, and LGMSG are required by the IMS DB/DC system for message queuing. Space requirements for message queue data sets vary with the system environment.

For SHMSG and LGMSG, up to 10 data sets can be provided for each. Multiple message queue data sets provide for configuration flexibility and performance.

IMS.QBLKSL, IMS.SHMSGL, IMS.LGMSGL

QBLKSL, SHMSGL, and LGMSGL are used only in an XRF complex; these data sets are similar in function to the regular message queue data sets. These data sets are always cold started and used as local message queues on an XRF alternate subsystem, from startup until completion of takeover, when the regular message queues become available. The DCB specification for the local message queue data sets must match the regular message queue data sets. However, the local message queues can be much smaller. The local message queues must be large enough to hold the shutdown message margin, plus primary and secondary IMS master terminal messages until they are dequeued.

IMS.RDS

The restart data set (RDS) contains information required for recovery, including the checkpoint ID table required for restarting IMS. The RDS also contains OSAM and VSAM buffer pool definition changes made by the UPDATE POOL TYPE(DBAS) command to be retained across emergency restart. However, RDS does not contain any log records.

This data set has the following attributes:

DSORG

Sequential

RECFM

Determined by IMS

LRECL

Determined by IMS

BLKSIZE

Determined by IMS

The BLKSIZE value is set to the buffer size as specified in the RDS= parameter in the DFSPBxxx member of the IMS PROCLIB data set or in JCL. The default is 4 KB.

You should allocate a minimum of one cylinder of contiguous tracks to this data set. The data set must be allocated large enough to contain at least 90 blocks reserved for RDS1 components BCPT, RRE, SIDX, and LCRE.

IMS.RDS2

RDS2 is used only in an XRF complex; this data set is identical in function to IMS.RDS.

You should allocate a minimum of one cylinder of contiguous tracks to this data set. The data set must be allocated large enough to contain at least 90 blocks reserved for RDS1 components BCPT, RRE, SIDX, and LCRE.

Do not manage either RDS with a migration or recall system that might recall the data set to a volume other than the one to which it was originally allocated. If you do so, IMS might be unable to warm start or emergency start the system.

IMS.RECON1, IMS.RECON2, IMS.RECON3

RECON1, RECON2, and RECON3 data sets contain system restart and recovery information managed by the Database Recovery Control (DBRC) function.

IMS.REFERAL

REFERAL contains intermediate text copies of descriptions supplied to the MFS Language utility.

IMS.SYSOnnn

The SYSOnnn DASD data sets are used to store spool SYSOUT data. The contents of these data sets can be printed using the SPOOL SYSOUT Print utility. This utility is either scheduled automatically or must be submitted manually, depending upon an option in the LINEGRP system definition macro. nnn is a one- to three-digit suffix assigned sequentially by IMS during system definition.

These data sets must be allocated as a single extent (contiguous tracks). Secondary allocation must not be specified.

These data sets must be initialized before they are used by IMS. For example, these data sets can be allocated on the SYSUT2 DD statement for the IEBGENER utility. Use DD DUMMY for SYSUT1. Specify DCB attributes for both SYSUT1 and SYSUT2.

IMS.TFORMAT

TFORMAT contains the online MFS descriptors, created by the MFS Language utility, for MFSTEST (test mode) online execution.

This data set must be concatenated in front of FORMATA or FORMATB in the IMSTFMTA or IMSTFMTB DD statements in the IMS execution procedure.

If you change MFS formats online, two DD statements must point to this TFORMAT data set, or the DD statements can point to two separate TFORMAT data sets.

This data set must be allocated as a single extent (contiguous tracks). Secondary allocation must not be specified.