MEDIA
Operations Guide

These parameters define the location of data files for the MEDIA database, process server and certain default values.

Parameter format	Description
CENTRAL=``location''	defines the MEDIA database location.
DEFAULT=``value''	establishes default values for medium allocations and additions by the UNKNOWN feature and the MEDIA ADD command if no other default records are found.
SVR_CENTRAL=``location''	defines the MEDIA server share file location. All servers running in a cluster MUST use the same file.
SVR_HOME=``location''	defines the MEDIA server default home directory.

The CENTRAL parameter specifies the MEDIA database location²⁰. This directory contains the files MEDIA.DAT, *.SDR, *.TDR and *.BJL which make up the MEDIA database. This is useful in a group of machines that are DECnetted together and you want one of the nodes to be the repository for all the MEDIA data files. For example you want node ABC to be the repository.

MEDIAS>SET CENTRAL == "ABC""ACCOUNT PASSWORD""::$2$DUA0:[MEDIA_DATA]"

The "ACCOUNT PASSWORD" access string is needed to give the local copy of the MEDIA.EXE image full access to the remote database. The program will then in turn check whether the local user has access to the requested medium.

The DEFAULT parameter designates the default values for certain medium attributes. These default values are used when the medium is allocated to a user by the /NEW (or UNKNOWN) feature and when media are added to the database by the MEDIA ADD command. ²¹

You should set these values to the most common type of media used at your site. The four media attributes are: DEFAULT_TYPE, DEFAULT_LOCATION, DEFAULT_DENSITY, and DEFAULT_LENGTH. For example, at your site the most common type²²

of medium is 2400 foot tapes written at 6250 bpi and stored in the LIBRARY. To establish these defaults use the following commands.

MEDIAS> SET DEFAULT_TYPE == TAPE MEDIAS> SET DEFAULT_LOCATION == LIBRARY MEDIAS> SET DEFAULT_DENSITY == 6250 MEDIAS> SET DEFAULT_LENGTH == 2400

Any of these settings that are left off will not be used in the selection of an available medium. Leave out attributes that do not matter. i.e. if the storage location does not matter when a user requests a medium, and any location will do, just leave the DEFAULT_LOCATION blank.

The SVR_CENTRAL parameter allows you to relocate the MEDIA server data file from the default location ²³ to another location. If you reset this in a cluster environment, you must use the same file for all servers running in a cluster.

The SVR_HOME parameter specifies the home directory for the server process. All temporary command files created by the server during the process of submitting jobs into a batch queue are placed in this directory. In most cases the default value ²³ is satisfactory. For example, you want all these temporary files to be placed in a special directory. You would type in:

MEDIAS> SET SVR_HOME == "DUA0:[COMTEMP]"

In a cluster this directory needs to be equally accessible from all members of the cluster. It is also required that this directory specification not explicitly or implicitly include a logical name search list. Thus, such names as SYS$MANAGER: (in a cluster) cannot be used.

3.3.2.2.6 Operator communication controls

These parameters affect the system's communications with the OPERATOR. Two types of OPCOM messages can be automatically generated.

Parameter format	Default	Description
COMPLETION=0 (no) or 1 (yes)	1	controls whether a message is sent to the operator on completion of a MEDIA_JOB.
OPCOM=0 (no) or 1 (yes)	0	specifies whether a message is sent to the operator on submission of a tape job.

The COMPLETION parameter controls whether a message is sent to the OPERATOR on completion of a MEDIA JOB. To set this parameter you would enter:

MEDIAS> SET COMPLETION == 1

The OPCOM parameter tells the system whether or not to send a message to the OPERATOR when a tape job is submitted into a queue for execution. To change this setting you would enter:

MEDIAS> SET OPCOM == 0

3.3.2.3 BCKMGR params

These parameters affect BCKMGR and control the database location, the calendar and the activity of the server process.

3.3.2.3.1 Database location control

The entire BCKMGR database is located using this one parameter. ²⁵

Parameter format	Description
BGR_CENTRAL=``location''	defines the BCKMGR database location.

The BCKMGR database is composed of the files BCKMGR.DAT and BGR_*.DAT. This is useful if you want to separate the BCKMGR database from other files on your system. In a cluster it must be accessible from all nodes. For example, you want to use a separate disk for these files:

MEDIAS> SET BGR_CENTRAL == "DISK$ISE0:[BCKMGR]"

After setting this parameter be sure to move all data files to this new location and restart the server. ²⁶

3.3.2.4 Vault parameters

The following parameters control how VAULT locates its DATABASE. The VAULT database is compose of a group of files that all have the extension .ADR.

Parameter format	Description
VDISK_DDDD=``location''	defines the location of the portions of the VAULT database that pertain to disk ``dddd''.
VLT_CENTRAL=``location''	defines the location of the top level VAULT database and areas not defined by the VDISK parameter.

The VDISK parameter specifies where to store VAULT information regarding files backed up from a particular disk. VDISK can be used to partition the ADR files created by VAULT across several disk drives thus distributing both the space occupied and the I/O load created during update operations. ²⁶

directories avoids the performance drop encountered when a VMS directory has in excess of 2,000 file entries.)

The procedure BCKMGR_MAINT.COM automatically sets up values for the VDISK parameter. It sets these values to point to subdirectories of the MEDIA_LIBRARY: directory. As a result you may not need to set these parameters.

For example, you want to place all files from disk ISE0 and ISE1 into subdirectories on the system disk. To do this you would enter:

MEDIAS> SET VDISK_DISK$ISE0 == "DISK$SYS:[VAULT.ISE0]" MEDIAS> SET VDISK_DISK$ISE1 == "DISK$SYS:[VAULT.ISE1]"

The DISK$ISE0 in the parameter name VDISK_DISK$ISE0 is the logical volume name ²⁷

of the disk drive in question. This splits the ADR files backed up from DISK$ISE0 and DISK$ISE1 and stores them in separate directories on DISK$SYS, called [VAULT.ISE0] and [VAULT.ISE1] respectively.

The VLT_CENTRAL parameter is a means of locating the top level files. These files are called 000000000.ADR and 000000001.ADR. The default location for these files is in the MEDIA_LIBRARY:. For example, you would like these files to appear in a special directory. To do so you would enter:

MEDIAS> SET VLT_CENTRAL == "DISK$SYS:[VAULT]"

3.3.3 Changing the parameter file

at the VMS prompt:

$ MEDIAS

The three most common commands that you will be using are SET, SHOW and HELP. Only the SET is described in detail in this section. The command formats for changing parameter settings are:

MEDIAS> SET/PARAMETER parameter = "value" MEDIAS> SET/PARAMETER parameter == "value"

The use of a single = indicates a change to the MEDIA.VAR (or node specific) file. The use of a double == indicates a change to the MEDIA2.VAR (or cluster common) file.

The SET command can also be used to change device availability by means of device qualifiers, using the format:

MEDIAS> SET/DEVICE device_name/qualifier

The SHOW command can be used to see the current parameter settings and device attributes. The command format to view a parameters is:

MEDIAS> SHOW/PARAMETER parameter_name

Wildcards can be used in the parameter name. For example specifying an * will list all the set parameters. The command format to view device attributes is:

MEDIAS> SHOW/DEVICE device_name

Wildcards can be used in the device name. For example specifying an * will list all the devices known to the server.

3.3.3.1 Qualifiers for the MEDIAS SET command

The MEDIAS SET command is used to change both parameter values and device attributes.

Qualifier		Function
/PARAMETER		specifies that a parameter value is to be changed. This is the default qualifier.
	/NORESTART	suppress the automatic restarting of the server process that normally occurs on exit after modifying a parameter.
/DEVICE		indicates a device attribute. If the device is already in use the command waits for the device to be released.
	/AVAILABLE	marks the device as available to the MEDIA system for allocation.
	/UNAVAILABLE	marks the device as unavailable to the MEDIA system for allocation. This does not prevent a device from being used by other VMS program
	/LOCK	forces the server process to allocate the device when not in use by a job or user.
	/UNLOCK	prevents the server process from allocating unused devices.
	/RESET	clears the information kept by the server about what was last mounted on a device.
	/UNLOAD	triggers an unload sequence on an on-line device.

3.3.3.2 Setting system-wide configuration choices

As installed, the INTERACTIVE parameter is set to 1, allowing device commands to be executed in interactive mode. Setting this parameter to 0 disables interactive execution of device commands. This forces³⁰ all medium operations to be done in a batch mode. The batch mode is used by the MEDIA job commands. ³¹

To disallow all interactive use of the MEDIA device commands you enter the following command:

MEDIAS> SET INTERACTIVE == 0

To prevent a user from being able to use the VMS ALLOCATE command to use a drive interactively anyway you can tell the MEDIA server to hold all drives that are not in use by entering:

MEDIAS> SET/DEVICE */LOCK

3.3.3.3 Setting defaults

A user will usually obtain a medium from the available pool using a command of the following format:

$ MEDIA MY_NAME_FOR_TAPE/NEW SET/COMMENT="Test 23 data"

The user could also have specified any of the /TYPE, /LOCATION, /DENSITY or /LENGTH qualifiers to control what type of medium is actually allocated. If these qualifiers are not used then the current setting of the DEFAULT parameter is used to determine the complete selection criteria. For example, you could have set them up as follows:

MEDIAS> SET DEFAULT_TYPE == REELTAPE MEDIAS> SET DEFAULT_LOCATION == USER_RACK MEDIAS> SET DEFAULT_DENSITY == 6250 MEDIAS> SET DEFAULT_LENGTH == 2400

Whenever you use the MEDIA ADD or MEDIA CATALOG commands all the data fields that you do not specify by the use of a qualifier are picked up from a default record stored in the database. All the default records are associated with a username DEFAULT and are given external ids. to match their purpose. For example DEFTAPE is the default for a new tape entry.³²

These default records are created by using the commands:

$ MEDIA DEFAULT_NAME ADD/USER=DEFAULT/QUALIFIERS

The most useful default value qualifiers are:

Qualifier	Meaning
/DENSITY=n	establishes the density setting for a tape reel.Known values are 800, 1600, 3200, 6250, 6666, 10000, 39782, 42500 79564
/LENGTH=n	establishes the length of a tape (in feet).
/LOCATION=``text''	establishes the physical storage location of the newly added medium.
/TYPE=``text''	establishes the TYPE characteristic of a newly added medium.

For example, at your site all new tapes are typically going to be used at 6250 bpi and as REELTAPE's. To set up this default record you enter:

$ MEDIA DEFTAPE ADD/USER=DEFAULT/TYPE=REELTAPE/DENSITY=6250

For another example, your site's cartridges are TK50s with a bpi of 6666.

$ MEDIA DEFCART ADD/USER=DEFAULT/TYPE=TK50/DENSITY=6666