docs: add scan assets

docs/docs/advanced/air-gap.md

@@ -37,7 +37,7 @@ GitHub Container Registry | <ul><li>`ghcr.io`</li><li>`pkg-containers.githubuser
 
 ### Self-hosting
 
-You can host Trivy's databases in your own container registry. Please refer to [Self-hosting document](./self-hosting.md#oci-databases) for a detailed guide.
+You can host Trivy's databases in your own container registry. Please refer to [Self-hosting document](../scan-asset/self-hosting.md#oci-databases) for a detailed guide.
 
 ## Embedded Checks
 
@@ -60,7 +60,7 @@ For more information about GitHub connectivity (including specific IP addresses)
 
 ### Self-hosting
 
-You can host a copy of VEX Hub on your own internal server. Please refer to the [self-hosting document](./self-hosting.md#vex-hub) for a detailed guide.
+You can host a copy of VEX Hub on your own internal server. Please refer to the [self-hosting document](../scan-asset/self-hosting.md#vex-hub) for a detailed guide.
 
 ## Maven Central / Remote Repositories
 

docs/docs/configuration/cache.md

@@ -10,7 +10,16 @@ The cache directory includes
 The cache option is common to all scanners.
 
 ## Clear Caches
-`trivy clean` subcommand removes caches.
+`trivy clean` command removes caches. You can select which cache component to remove:
+
+| option	         | description                                                 |
+|-----------------|-------------------------------------------------------------|
+| -a/--all        | remove all caches                                           |
+| --checks-bundle | remove checks bundle                                        |
+| --java-db       | remove Java database                                        |
+| --scan-cache    | remove scan cache (container and VM image analysis results) |
+| --vex-repo      | remove VEX repositories                                     |
+| --vuln-db       | remove vulnerability database                               |
 
 ```bash
 $ trivy clean --scan-cache
@@ -25,8 +34,6 @@ $ trivy clean --scan-cache
 
 </details>
 
-If you want to delete cached vulnerability databases, use `--vuln-db`.
-You can also delete all caches with `--all`.
 See `trivy clean --help` for details.
 
 ## Cache Directory

docs/docs/configuration/scan-assets.md

@@ -0,0 +1,66 @@
+# Scan Assets
+
+This document describes how to configure Trivy's scan asset management behavior.
+While assets are automatically managed by default, there are various configuration options available for specific needs.
+
+For details about the scan assets, see [Scan Assets](../scan-asset/index.md).
+
+## Custom Locations
+
+You can configure custom download locations for each asset:
+
+| Asset            | Configuration Method         | Available Options                                                 |
+|------------------|------------------------------|-------------------------------------------------------------------|
+| Vulnerability DB | `--db-repository`            | [OCI Repositories](../scan-asset/index.md#vulnerability-database) |
+| Java DB          | `--java-db-repository`       | [OCI Repositories](../scan-asset/index.md#java-index-database)    |
+| Checks Bundle    | `--checks-bundle-repository` | [OCI Repositories](../scan-asset/index.md#checks-bundle)          |
+| VEX Repository   | [repository.yaml][vex-repo]  | [Any VEX repositories][vex-repo]                                  |
+
+For details about hosting options, see [Self-Hosting Assets](../scan-asset/self-hosting.md)
+
+Example usage for OCI registry configuration:
+
+``` bash
+trivy image --db-repository registry.my-company.example/trivy-db:2 alpine:3.15
+```
+
+Multiple repositories can be specified as fallbacks for OCI assets:
+
+```bash
+trivy image --db-repository registry.my-company.example/trivy-db:2 --db-repository ghcr.io/aquasecurity/trivy-db:2 alpine:3.15
+```
+
+## Skip Updates
+
+| Asset            | Skip Flag                | Description                         |
+|------------------|--------------------------|-------------------------------------|
+| Vulnerability DB | `--skip-db-update`       | Skip vulnerability database updates |
+| Java DB          | `--skip-java-db-update`  | Skip Java database updates          |
+| Checks Bundle    | `--skip-check-update`    | Skip policy bundle updates          |
+| VEX Hub          | `--skip-vex-repo-update` | Skip VEX repository updates         |
+
+For example,
+
+```bash
+trivy image --skip-db-update --skip-java-db-update debian:12
+```
+
+## Update Only Mode
+
+| Asset            | Update Command/Flag       | Description                          |
+|------------------|---------------------------|--------------------------------------|
+| Vulnerability DB | `--download-db-only`      | Download vulnerability database only |
+| Java DB          | `--download-java-db-only` | Download Java database only          |
+| Checks Bundle    | N/A                       | No dedicated download-only flag      |
+| VEX Hub          | `trivy vex repo download` | Download VEX data explicitly         |
+
+For example,
+
+```bash
+trivy image --download-db-only
+```
+
+## Cache Cleanup
+See [Clear Caches](./cache.md#clear-caches)
+
+[vex-repo]: ../supply-chain/vex/repo.md