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+# Sync Interface User Guide
+
+## Overview
+
+The Sync Interface allows you to synchronize data from Autotask to your PostgreSQL database. This guide explains each sync option, when to use it, and what to expect.
+
+## Sync Interface Location
+
+Access the sync interface at: **Admin Dashboard → Sync Controls**
+
+---
+
+## Sync Options
+
+### 1. **Full Sync** 🔄
+
+**What it does:**
+- Syncs **all entities** from Autotask to PostgreSQL
+- Fetches all active records for each entity type
+- **Soft-deletes** records that exist in your database but are no longer in Autotask
+- Respects the date range filter for time-based entities (Tickets, Tasks, Projects)
+
+**When to use:**
+- **Initial setup** - First time syncing your Autotask data
+- **Data recovery** - After database issues or data corruption
+- **Periodic refresh** - Monthly or quarterly to ensure data consistency
+- **After major Autotask changes** - When records have been bulk-deleted or modified in Autotask
+
+**Important notes:**
+- ⚠️ **Requires confirmation** - Shows a warning dialog before starting
+- ⏱️ **Takes longest** - Can take 10-30 minutes depending on data volume
+- 🗑️ **Soft-deletes missing records** - Sets `is_deleted = true` for records not found in Autotask
+- 📅 **Respects date range** - For Tickets/Tasks/Projects, only syncs within selected date range
+
+**Example use case:**
+> "It's the first Monday of the month. I want to ensure all our data is fresh and any deleted records in Autotask are marked as deleted in our database."
+
+**What gets synced (in order):**
+1. Companies
+2. Resources (Users)
+3. Statuses
+4. Issue Types
+5. Sub-Issue Types
+6. Work Types
+7. Contacts
+8. Projects
+9. Tickets (within date range)
+10. Tasks (within date range)
+11. Configuration Items
+12. Contracts
+13. Billing Items
+14. Time Entries (within date range)
+
+---
+
+### 2. **Incremental Sync** ⚡
+
+**What it does:**
+- Syncs **only records modified since the last sync**
+- Uses Autotask's `lastModifiedDate` field to filter records
+- Much faster than Full Sync
+- Does **NOT** soft-delete missing records
+
+**When to use:**
+- **Daily updates** - Regular scheduled syncs to keep data current
+- **Quick refresh** - After making changes in Autotask
+- **Automated syncs** - Set up on a cron schedule (e.g., every 4 hours)
+- **Low-impact updates** - When you need fresh data without heavy processing
+
+**Important notes:**
+- ✅ **No confirmation needed** - Starts immediately
+- ⚡ **Fast** - Typically completes in 1-5 minutes
+- 🔄 **Additive only** - Adds/updates records but doesn't delete
+- 📊 **Best for routine updates** - Ideal for keeping data fresh
+
+**Example use case:**
+> "A technician just closed several tickets in Autotask. I want to pull those updates into our dashboard without running a full sync."
+
+**How it works:**
+1. Checks `sync_history` table for last successful sync of each entity
+2. Queries Autotask for records where `lastModifiedDate > last_sync_time`
+3. Updates existing records or inserts new ones
+4. Skips entities that have no modifications
+
+---
+
+### 3. **Chunked Tickets** 📦
+
+**What it does:**
+- Syncs **only Tickets** in monthly date chunks
+- Breaks large date ranges into manageable pieces
+- Prevents API timeouts and memory issues
+- Shows real-time progress for each chunk
+
+**When to use:**
+- **Large date ranges** - Syncing 3+ years of ticket history
+- **Initial ticket sync** - First time pulling historical tickets
+- **Timeout prevention** - When regular ticket sync fails with timeouts
+- **Off-hours processing** - Running overnight syncs for historical data
+
+**Important notes:**
+- 📊 **Progress tracking** - Shows which month is currently syncing
+- 🔄 **Resilient** - Continues even if individual chunks fail
+- 🎯 **Tickets only** - Does not sync other entities
+- ⏱️ **Slower but reliable** - Takes longer but handles large datasets
+
+**Example use case:**
+> "I need to sync 5 years of ticket history. A regular sync times out, so I'll use Chunked Tickets to process it month by month."
+
+**How it works:**
+1. Calculates monthly chunks based on selected date range
+2. Processes each month sequentially (e.g., "Jan 2024", "Feb 2024", etc.)
+3. Shows progress: "Processing chunk 15/60: Mar 2023"
+4. Continues even if some months fail (logs failures)
+5. Displays final summary with total records processed
+
+**Date range examples:**
+- Last 7 Days → ~1 chunk
+- Last 2 Years → ~24 chunks
+- Last 5 Years → ~60 chunks
+- All Time → Could be 100+ chunks
+
+---
+
+### 4. **Sync Selected** 🎯
+
+**What it does:**
+- Syncs **only the entities you select** from the entity list
+- Full sync for selected entities (not incremental)
+- Respects date range for time-based entities
+- Does **NOT** soft-delete missing records
+
+**When to use:**
+- **Targeted updates** - Only need to refresh specific entities
+- **Dependency sync** - Sync Companies before syncing Tickets
+- **Troubleshooting** - Re-sync a specific entity that had errors
+- **Testing** - Verify sync works for a single entity
+
+**Important notes:**
+- ✅ **Requires entity selection** - Must select at least one entity
+- 🎯 **Selective** - Only syncs what you choose
+- ⚠️ **Respect dependencies** - Ensure parent entities are synced first
+- 📅 **Uses date range** - For Tickets/Tasks/Projects
+
+**Example use case:**
+> "We just imported 50 new companies into Autotask. I only need to sync Companies and Contacts, not everything else."
+
+**Entity dependencies to consider:**
+- **Contacts** → Requires Companies
+- **Tickets** → Requires Companies, Resources, Contacts
+- **Tasks** → Requires Resources, Projects, Tickets
+- **Configuration Items** → Requires Companies, Contacts
+- **Time Entries** → Requires Companies, Resources, Projects, Tasks, Tickets
+
+**How to use:**
+1. Click entity checkboxes to select (e.g., Companies, Contacts)
+2. Set date range if syncing time-based entities
+3. Click "Sync Selected (2)" button
+4. Monitor progress in sync history
+
+
+---
+
+## Date Range Selector 📅
+
+**Applies to:** Tickets, Tasks, Projects, Time Entries
+
+**Available ranges:**
+- **Last 7 Days** (0.019 years) - Quick updates, minimal data
+- **Last 30 Days** (0.082 years) - Monthly refresh
+- **Last 90 Days** (0.25 years) - Quarterly data
+- **Last 1 Year** - Recent history
+- **Last 2 Years** ⭐ **Recommended** - Good balance of history and performance
+- **Last 3 Years** - Extended history
+- **Last 5 Years** - Long-term analysis
+- **Last 10 Years** - Comprehensive history
+- **All Time** ⚠️ - Complete history (very slow, use off-hours)
+
+**Why limit date ranges?**
+1. **Performance** - Fewer records = faster sync
+2. **API limits** - Autotask has rate limits and timeout thresholds
+3. **Relevance** - Most reporting focuses on recent data
+4. **Resource usage** - Large syncs consume more memory and CPU
+
+**Recommendation:**
+- **Daily syncs:** Last 7-30 Days
+- **Weekly syncs:** Last 90 Days
+- **Monthly syncs:** Last 1-2 Years
+- **Initial setup:** Last 2 Years, then run "All Time" overnight if needed
+
+---
+
+## Entity Selector
+
+**Available entities:**
+
+| Entity | Description | Dependencies |
+|--------|-------------|--------------|
+| **Companies** | Customer/vendor organizations | None |
+| **Resources** | Autotask users/technicians | None |
+| **Statuses** | Ticket/task statuses | None |
+| **Issue Types** | Ticket categorization | None |
+| **Sub-Issue Types** | Ticket sub-categories | None |
+| **Work Types** | Time entry work types | None |
+| **Contacts** | People at companies | Companies |
+| **Projects** | Customer projects | Companies, Resources |
+| **Tickets** | Support tickets | Companies, Resources, Contacts |
+| **Tasks** | Project/ticket tasks | Resources, Projects, Tickets |
+| **Configuration Items** | Assets/devices | Companies, Contacts |
+| **Contracts** | Service agreements | Companies, Contacts |
+| **Billing Items** | Billable items | Companies, Tasks, Tickets, Projects |
+| **Time Entries** | Time tracking | Companies, Resources, Projects, Tasks, Tickets |
+
+**Selection tips:**
+- ✅ **Select dependencies first** - e.g., Companies before Contacts
+- 🔄 **Use "Select All"** for full sync
+- 🎯 **Deselect unneeded** - Skip entities you don't use
+- ⚠️ **Check order** - Entities sync in dependency order automatically
+
+---
+
+## Sync Progress & Monitoring
+
+### Real-time Progress
+- **Progress bars** - Visual indication of sync status
+- **Record counts** - Shows records added/updated/deleted
+- **Chunk tracking** - For chunked syncs, shows current month
+- **Error alerts** - Immediate notification of failures
+
+### Sync History Table
+- **Recent syncs** - Last 50 sync operations
+- **Status indicators** - ✅ Completed, ❌ Failed, ⏳ In Progress
+- **Timing data** - Duration and timestamps
+- **Error messages** - Detailed failure information
+- **Filter options** - By entity, status, or date
+
+### Background Processing
+- Syncs run in the **background** (server-side)
+- UI remains responsive during sync
+- Dashboard auto-refreshes every 30 seconds
+- Can close browser - sync continues on server
+
+---
+
+## Best Practices
+
+### Daily Operations
+```
+Morning: Incremental Sync (Last 7 Days)
+→ Fast refresh of overnight changes
+→ 2-5 minutes
+```
+
+### Weekly Maintenance
+```
+Monday: Full Sync (Last 90 Days)
+→ Ensure data consistency
+→ Clean up deleted records
+→ 10-15 minutes
+```
+
+### Monthly Deep Sync
+```
+First of Month: Full Sync (Last 2 Years)
+→ Comprehensive data refresh
+→ Historical accuracy
+→ 20-30 minutes
+```
+
+### Initial Setup
+```
+Step 1: Full Sync (Last 2 Years)
+→ Get recent operational data
+→ 20-30 minutes
+
+Step 2: Chunked Tickets (All Time) - Optional
+→ Run overnight for complete history
+→ 1-3 hours depending on volume
+```
+
+---
+
+## Troubleshooting
+
+### "Sync is taking too long"
+**Solution:** Use Chunked Tickets for large date ranges
+- Switch from "All Time" to "Last 2 Years"
+- Use Chunked Tickets for historical data
+- Run large syncs during off-hours
+
+### "Sync failed with timeout error"
+**Solution:** Reduce scope
+- Decrease date range (e.g., from 5 years to 1 year)
+- Use Chunked Tickets instead of Full Sync
+- Sync entities individually using Sync Selected
+
+### "Missing records in database"
+**Solution:** Run Full Sync
+- Full Sync will fetch all active records
+- Check date range - records outside range won't sync
+- Verify records exist and are active in Autotask
+
+### "Deleted records still showing"
+**Solution:** Run Full Sync
+- Only Full Sync performs soft-deletes
+- Incremental and Entity syncs don't remove records
+- Check `is_deleted` flag in database
+
+### "Foreign key constraint errors"
+**Solution:** Sync dependencies first
+- Sync Companies before Contacts
+- Sync Resources before Tickets
+- Use Full Sync to handle dependencies automatically
+
+### "Some entities failed, others succeeded"
+**Check:** Sync History table
+- Review error messages for failed entities
+- Re-sync failed entities individually
+- Check Autotask API connectivity
+- Review logs: `npx tsx scripts/analyze-sync-failures.ts`
+
+---
+
+## Understanding Sync Results
+
+### Record Counts
+
+**Records Added** (+)
+- New records inserted into database
+- First time seeing this record from Autotask
+
+**Records Updated** (~)
+- Existing records modified
+- Changes detected from Autotask
+
+**Records Deleted** (-)
+- Records soft-deleted (Full Sync only)
+- Set `is_deleted = true` when not found in Autotask
+- Only happens during Full Sync
+
+### Example Results
+```
+✅ Companies: +5 ~23 -2
+   → 5 new companies
+   → 23 companies updated
+   → 2 companies soft-deleted (no longer in Autotask)
+
+✅ Tickets: +142 ~67 -0
+   → 142 new tickets
+   → 67 tickets updated
+   → 0 deleted (incremental sync doesn't delete)
+```
+
+---
+
+## Sync Timing Recommendations
+
+### Business Hours (9 AM - 5 PM)
+- ✅ Incremental Sync (Last 7-30 Days)
+- ✅ Sync Selected (specific entities)
+- ⚠️ Avoid Full Sync with large date ranges
+- ⚠️ Avoid Chunked Tickets for All Time
+
+### Off-Hours (Evening/Night)
+- ✅ Full Sync (Last 2+ Years)
+- ✅ Chunked Tickets (All Time)
+- ✅ Large historical syncs
+- ✅ Data recovery operations
+
+### Automated Schedule (Recommended)
+```
+Every 4 hours: Incremental Sync
+→ Keeps data fresh throughout the day
+
+Daily at 2 AM: Full Sync (Last 90 Days)
+→ Maintains data consistency
+
+Weekly Sunday 1 AM: Full Sync (Last 2 Years)
+→ Deep refresh and cleanup
+```
+
+---
+
+## API Rate Limits & Performance
+
+### Autotask API Limits
+- **Rate limit:** ~500 requests per hour per integration
+- **Timeout:** 60 seconds per request
+- **Page size:** 500 records maximum per page
+
+### Sync Performance Tips
+1. **Use Incremental Sync** for routine updates
+2. **Limit date ranges** to reduce API calls
+3. **Avoid concurrent syncs** - wait for one to finish
+4. **Use Chunked Tickets** for large datasets
+5. **Schedule heavy syncs** during off-hours
+
+### Estimated Sync Times
+
+| Sync Type | Date Range | Estimated Time |
+|-----------|------------|----------------|
+| Incremental | N/A | 2-5 minutes |
+| Full Sync | Last 7 Days | 5-10 minutes |
+| Full Sync | Last 90 Days | 10-15 minutes |
+| Full Sync | Last 2 Years | 20-30 minutes |
+| Chunked Tickets | Last 5 Years | 1-2 hours |
+| Chunked Tickets | All Time | 2-4 hours |
+
+*Times vary based on data volume and API performance*
+
+---
+
+## Analyzing Sync Failures
+
+Use the sync failure analysis script to investigate issues:
+
+```bash
+# Show failures from last 7 days
+npx tsx scripts/analyze-sync-failures.ts
+
+# Show all syncs from yesterday
+npx tsx scripts/analyze-sync-failures.ts --days 1 --all
+
+# Check specific entity failures
+npx tsx scripts/analyze-sync-failures.ts --days 30 --entity tickets
+
+# Show all completed syncs
+npx tsx scripts/analyze-sync-failures.ts --status completed --all
+```
+
+The script provides:
+- Failure summary by entity
+- Error categorization (NETWORK_ERROR, DATABASE_ERROR, etc.)
+- Success rate statistics
+- Detailed error messages
+- Timing information
+
+---
+
+## Quick Reference
+
+| Need | Use This | Time |
+|------|----------|------|
+| Quick update | Incremental Sync | 2-5 min |
+| Daily refresh | Incremental (Last 7 Days) | 2-5 min |
+| Weekly cleanup | Full Sync (Last 90 Days) | 10-15 min |
+| Monthly deep sync | Full Sync (Last 2 Years) | 20-30 min |
+| Initial setup | Full Sync (Last 2 Years) | 20-30 min |
+| Historical tickets | Chunked Tickets (All Time) | 1-3 hours |
+| Single entity | Sync Selected | 1-10 min |
+| After timeout | Chunked Tickets | Varies |
+| Data recovery | Full Sync (appropriate range) | Varies |
+
+---
+
+## Support & Additional Resources
+
+- **Sync Logging Documentation:** `docs/SYNC_LOGGING_IMPROVEMENTS.md`
+- **Analysis Script:** `scripts/analyze-sync-failures.ts`
+- **Sync History:** Admin Dashboard → Sync History Table
+- **Error Logs:** Check structured logs for detailed error information
+
+---
+
+## Summary
+
+**For most users:**
+- Run **Incremental Sync** daily for routine updates
+- Run **Full Sync** weekly/monthly for data consistency
+- Use **Chunked Tickets** for large historical syncs
+- Use **Sync Selected** for targeted entity updates
+
+**Remember:**
+- ✅ Incremental = Fast, additive only
+- 🔄 Full = Complete, includes soft-deletes
+- 📦 Chunked = Reliable for large datasets
+- 🎯 Selected = Targeted, specific entities
+
+**Date ranges matter:**
+- Smaller ranges = Faster syncs
+- Larger ranges = More complete data
+- Balance based on your needs and available time