The following general conditions must be observed when working with Net-Storage:
A file on Net-Storage consists of just one extent. Specification of a volume list is accepted, but only the first volume is used.
Storage space assignment can be specified in the SPACE operand of the CREATE-FILE and MODIFY-FILE-ATTRIBUTES commands, but no storage space of this size is occupied on Net-Storage. The (maximum) storage space assignment takes place only when the file is stored in the corresponding size.
With respect to allocation, a Net-Storage volume behaves like an NK2 disk with the minimum allocation unit of 8 KB.
Absolute allocation is not possible for files on Net-Storage.
Files with the following attributes cannot be created on a Net-Storage volume:
Files with a PAM key
Work files
Temporary files
File generation groups
The following applies to node files:
PAM node files are supported in BS2000 OSD/BC V10.0 and higher, SAM node files in BS2000 OS DX and higher. Further requirements such as hardware dependencies are described in the current Release Notices.
For BS2000, only the following files can become node files:
PAM files without a PAM key (BLK-CONTROL=NO)
SAM files without a PAM key (BLK-CONTROL=DATA) and with variable record length (REC-FORM=V)
Node files are structured and end on a byte boundary.
Node files must be imported to be processed in BS2000.
Node files have the following access rights in UFS for the user concerned:
rw- --- ---These are the minimum access rights required for BS2000 for the user concerned. A user of the open system can change these access rights. A BS2000 user cannot do this.
If the ownership or access rights (chown, chmod) are changed from the open systems side, BS2000 may possibly no longer be able to access the files.
From the BS2000 side node files can only be created and managed as normal files. For example, links cannot be imported into BS2000 as special aspects of processing UNIX links (hardware and software links) cannot be mapped in BS2000.
If node files are imported as SAM file, it is important to note the following:
At first, the file size is adopted from the file system into the catalog entry. From the BS2000 viewpoint, this value is a bit too small, because so far it ignores the SAM structure (block control fields and length fields plus unused bytes at the end of a block). The correct value is only determined when the file is opened and then updated in the catalog.
For the file, the maximum block size of (STD,16) is entered in the catalog. The maximum possible record length is calculated by subtracting the length of the block control field and the record length field from this value. This way, BS2000 can read records of up to 32768-20=32748 bytes from the node file. If the blocking factor is lower, the maximum record length that can be processed is appropriately smaller. Because of this, it is recommended to always use the maximum block size for SAM node files.
When copying (COPY-FILE) from node files, it is important to note the following:
When copying into a node file, the node file must have a corresponding catalog entry. If necessary, a catalog entry must be created using the CREATE-FILE command:
/CREATE-FILE <node-file>,SUPPORT=*PUBLIC-DISK(
STORAGE-TYPE=*NET-STORAGE(FILE-TYPE=*NODE))When a SAM is being copied into a node file, the user can specify the desired NETCSS in the CREATE-FILE command when the node file is created. The CSS is adopted from the source file (*NONE is equivalent to EDF03IRV).
If a SAM node file is copied into a SAM file, the NETCSS is not transferred.
If a SAM node file is copied into a SAM node file, the NETCCS is adopted from the source file.
The administrator of the file server can grant access to public files on Net-Storage for applications which run on different operating systems. The following must be borne in mind here:
Applications of foreign (non-BS2000) operating systems may only access BS2000 files on Net-Storage in read mode. They may access node files in write mode, too.
Users from an open system obtain access to node files by means of their user and group numbers (uid, gid). To enable joint access to node files, the user and group numbers of the BS2000 user and of the user in the open system must be coordinated. Under NFSv4 it is necessary to use a directory service (openLDAP or Active Directory) to do this.
Data access control in BS2000 (e.g. access only by the file owner, password protection) is effective only if access takes place from BS2000. This has no effect for accesses from open systems.