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URL: https://7po3j-syaaa-aaaal-qbqea-cai.icp0.io/advanced-concepts/system-apis/preupgrade-postupgrade.html
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Text Content

 1.  The Motoko Programming Language
 2.  
 3.  Part 1
 4.  1. Introduction
     ❱
 5.  1. 1.1. Getting Started
 6.  2. Common Programming Concepts
     ❱
 7.  1.  2.1. Variables
     2.  2.2. Mutability
     3.  2.3. Comments
     4.  2.4. Types
         ❱
     5.  1. 2.4.1. Tuples
         2. 2.4.2. Records
         3. 2.4.3. Variants
         4. 2.4.4. Immutable Arrays
         5. 2.4.5. Mutable Arrays
     6.  2.5. Operators
         ❱
     7.  1. 2.5.1. Numeric operators
         2. 2.5.2. Relational operators
         3. 2.5.3. Assignment operators
         4. 2.5.4. Text concatenation
         5. 2.5.5. Logical expressions
         6. 2.5.6. Bitwise operators
         7. 2.5.7. Operator precedence
     8.  2.6. Pattern Matching
     9.  2.7. Functions
     10. 2.8. Options and Results
     11. 2.9. Control Flow
         ❱
     12. 1. 2.9.1. If Expression
         2. 2.9.2. If Else Expression
         3. 2.9.3. Switch Expression
     13. 2.10. Objects and Classes
         ❱
     14. 1. 2.10.1. Objects
         2. 2.10.2. Classes
     15. 2.11. Modules and Imports
     16. 2.12. Assertions
 8.  3. Internet Computer Programming Concepts
     ❱
 9.  1. 3.1. Actors
        ❱
     2. 1. 3.1.1. From Actor to Canister
        2. 3.1.2. Canister Calls from Clients
     3. 3.2. Principals and Authentication
     4. 3.3. Async Data
        ❱
     5. 1. 3.3.1. Shared Types
        2. 3.3.2. Candid
     6. 3.4. Basic Memory Persistence
        ❱
     7. 1. 3.4.1. Upgrades
        2. 3.4.2. Stable Variables
 10. 
 11. Part 2
 12. 4. Advanced Types
     ❱
 13. 1. 4.1. Generic Types
     2. 4.2. Subtyping
     3. 4.3. Recursive Types
     4. 4.4. Type Bounds
 14. 5. The Base Library
     ❱
 15. 1. 5.1. Primitive Types
        ❱
     2. 1.  5.1.1. Bool
        2.  5.1.2. Nat
        3.  5.1.3. Int
        4.  5.1.4. Float
        5.  5.1.5. Principal
        6.  5.1.6. Text
        7.  5.1.7. Char
        8.  5.1.8. Bounded Number Types
            ❱
        9.  1. 5.1.8.1. Nat8
            2. 5.1.8.2. Nat16
            3. 5.1.8.3. Nat32
            4. 5.1.8.4. Nat64
            5. 5.1.8.5. Int8
            6. 5.1.8.6. Int16
            7. 5.1.8.7. Int32
            8. 5.1.8.8. Int64
        10. 5.1.9. Blob
     3. 5.2. Utility Modules
        ❱
     4. 1. 5.2.1. Iterators
        2. 5.2.2. Hash
        3. 5.2.3. Option
        4. 5.2.4. Result
        5. 5.2.5. Order
        6. 5.2.6. Error
        7. 5.2.7. Debug
     5. 5.3. Data Structures
        ❱
     6. 1. 5.3.1. Array
        2. 5.3.2. List
        3. 5.3.3. Buffer
        4. 5.3.4. HashMap
        5. 5.3.5. RBTree
     7. 5.4. More Data Structures
     8. 5.5. IC APIs
        ❱
     9. 1. 5.5.1. Time
        2. 5.5.2. Timer
        3. 5.5.3. CertifiedData
        4. 5.5.4. Random
        5. 5.5.5. Experimental
 16. 6. Advanced Concepts
     ❱
 17. 1. 6.1. Async Programming
     2. 6.2. Scalability
        ❱
     3. 1. 6.2.1. Actor Classes
        2. 6.2.2. Stable Storage
     4. 6.3. System API's
        ❱
     5. 1. 6.3.1. Message Inspection
        2. 6.3.2. Timers
        3. 6.3.3. Certified Variables
        4. 6.3.4. Pre-upgrade and Post-upgrade
        5. 6.3.5. Cryptographic Randomness
 18. 
 19. Part 3
 20. 7. Project Deployment
     ❱
 21. 1. 7.1. Installing the SDK
     2. 7.2. Local Deployment
     3. 7.3. Canister Status
     4. 7.4. Identities and PEM Files
     5. 7.5. Cycles and ICP
     6. 7.6. Cycles Wallet
     7. 7.7. IC Deployment
 22. 8. Common Internet Computer Canisters
     ❱
 23. 1. 8.1. IC Management Canister
     2. 8.2. ICP Ledger Canister
     3. 8.3. Cycle Minting Canister
 24. 9. Internet Computer Standards
     ❱
 25. 1. 9.1. ICRC1
 26. 10. Tokenized Comments Example
 27. 
 28. APPENDIX
 29. 11. TABLES


 * Light
 * Rust
 * Coal
 * Navy
 * Ayu


THE MOTOKO PROGRAMMING LANGUAGE BOOK





PRE-UPGRADE AND POST-UPGRADE

For a demonstration of the use of the preupgrade and postupgrade system
functions, see the tokenized comments example.

> NOTE
> preupgrade and postupgrade system functions may trap during execution and data
> may be lost in the process. Work is underway to improve canister upgrades by
> working with stable storage.