Using Caché Multi-Dimensional Storage - InterSystems ...

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Global Structure An operation on ^Data can retrieve its entire contents with a minimum number of disk operations. There are a number of additional techniques used to ensure that inserts, updates, and deletes are performed efficiently. 2.3 Referencing Globals A global resides within a particular Caché database. Portions of a global can reside in different databases if appropriate mappings are used. A database can by physically located on the current system, or on a remote system accessed through Caché networking. The term dataset refers to the system and the directory that contain a Caché database. For further details on networking, see the Distributed Data Management Guide. A namespace is a logical definition of the datasets and global mappings that together form a set of related information. A simple global reference applies to the currently selected namespace. The namespace definition can cause this to physically access a database on the local system or a remote system. Different globals can be mapped to different locations or datasets (where a dataset refers to the system and the directory that contain a Caché database). For example, to create a simple reference to the global ORDER in the namespace to which it currently has been mapped, use the following syntax: ^ORDER 2.3.1 Setting Global Mapping You can map globals and routines from one database to another on the same or different systems. This allows simple references to data which can exist anywhere and is the primary feature of a namespace. You can map whole globals or pieces of globals. This ability to map global subscripts allow data to easily span disks. To establish this type of mapping, see the “Add Global, Routine, and Package Mapping to a Namespace” section of the “Configuring Caché” chapter of the Caché System Administration Guide. Once you've mapped a global from one namespace to another, you can reference the mapped global as if it were in the current namespace — with a simple reference. For example: ^ORDER 10 Using Caché Multi-Dimensional Storage
Referencing Globals 2.3.2 Extended Global References You can refer to a global located in a namespace other than the current namespace. This is known as an extended global reference or simply an extended reference. There are two forms of extended references: • Explicit namespace reference — You specify the name of the namespace where the global is located as part of the syntax of the global reference. • Implied namespace reference — You specify the directory and, optionally, the system name as part of the syntax of the global reference. In this case, no global mappings apply, since the physical dataset (directory and system) is given as part of the global reference. The use of explicit namespaces is preferred, because this allows for redefinition of logical mappings externally, as requirements change, without altering your application code. Caché supports two forms of extended references: • Bracket syntax, which encloses the extended reference with square brackets ([ ]). • Environment syntax, which encloses the extended reference with vertical bars (| |). 2.3.2.1 Bracket Syntax You can use bracket syntax to specify an extended global reference with either an explicit namespace or an implied namespace: Explicit namespace: ^[nspace]glob Implied namespace: ^[dir,sys]glob In an explicit namespace reference, nspace is a defined namespace that the global glob has not currently been mapped or replicated to. In an implied namespace reference, dir is a directory, sys is a system, and glob is a global within that directory. You must include quotation marks around the directory and system names or the namespace name unless you specify them as variables. The directory and system together comprise an implied namespace. An implied namespace can reference either: • The specified directory on the specified system. Using Caché Multi-Dimensional Storage 11
Page 1 and 2: Using Caché Multi-Dimensional Stor
Page 3 and 4: Table of Contents 1 Introduction ..
Page 5: List of Tables Bit String Operation
Page 8 and 9: Introduction ^Settings("Auto1","Pro
Page 10 and 11: Introduction 1.3 Use in Application
Page 12 and 13: Global Structure • The other char
Page 14 and 15: Global Structure 5. A bitstring. In
Page 18 and 19: Global Structure • The specified
Page 21 and 22: 3 Using Multidimensional Storage (G
Page 23 and 24: If you are using Caché ObjectScrip
Page 25 and 26: Testing the Existence of a Global N
Page 27 and 28: Traversing Data within a Global Set
Page 29 and 30: Traversing Data within a Global 3.5
Page 31 and 32: Temporary Globals The default stora
Page 33 and 34: Sorting Data within Globals 3.9.2 N
Page 35 and 36: Managing Transactions // Erase any
Page 37 and 38: 2. Acquire a lock (or locks) on the
Page 39 and 40: level using a naked global referenc
Page 41 and 42: 4 SQL and Object Use of Multidimens
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Page 45 and 46: Data /// A LineItem class Class MyA
Page 47 and 48: Bitmap Indices Note the following t
Page 49 and 50: Bitmap Indices CHAIR 0 0 1 1 0 HAT

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